Who does not know the vast importance which our illustrious Cuvier attributed in the progress of the natural system, to him who first conceived the idea of preserving objects in alcohol?
(Gannal and Harlan 1840)
Fluid Preservation in the Ancient World
The idea of preserving organic material by submerging it in a fluid is very old. Vinegar (acetic acid) has long been used by humans to preserve food as it is sufficiently acidic to afford protection against bacteria, and many cultures figured out how to store food long-term in sealed containers of vinegar, honey, oil, or brine (Shephard 2000). A concentration of about 15 percent acetic acid will stop bacterial growth, but most vinegar contains only 4–5 percent acetic acid, so salt and spices containing volatile oils were usually added to the vinegar to strengthen its preservative properties (Anderson 1925). Herodotus (ca. 484–425 BCE) reported that the Egyptians consumed “wine . . . made of barley” and ate fish that had been preserved by being “pickled in brine” (Grene 1987, 163–164). Greek and Roman writings mention the preservation of fish products using vinegar (Anderson 1925).
Before the Egyptians had perfected mummification, the Babylonians figured out one of the secrets of successful long-term preservation—keep oxygen away from the tissues, which they accomplished by submerging bodies in honey (Grene 1987; Ransome 1937). According to tradition, submersion in honey is how the body of Alexander the Great (356–323 BCE) was preserved for the two-year journey back to Egypt after his death in Babylon in 323 BCE (Ransome 1937). The bodies of the Spartan king, Agesipolis (400–360 BCE), and the philosopher Democritus (460–370 BCE) were also preserved in honey (Ransome 1937). As part of the mummification process, the Egyptians sometimes preserved the important organs of the body in oil in canopic jars (El Mahdy 1989). The important organs did not include the brain, which they thought (as did Aristotle) was only good for producing mucous (French 1994).
History of Ethyl Alcohol
Ethyl alcohol is one of the oldest known organic chemicals, long accessible to humans from natural fermentation processes (Monick 1968), and later from controlled fermentation processes used to produce alcoholic beverages. Archaeological evidence indicates that the production of beer (fermented grain) and mead (fermented honey) preceded the production of wine (fermented grapes) (Amerine 1964). The production of beer and wine is depicted on Sumerian pottery from 4200 BCE. There is chemical evidence for beer production from the Godin Tepe site in the Zagros Mountains of Iran (Michel et al. 1992) in the form of carbonized barley and calcium oxalate deposits (a by-product of brewing barley beer) in the grooves of beer jars. However, the oldest evidence for the preparation of a fermented alcohol beverage dates to at least nine thousand years ago in China (McGovern 2009).
The problem with fermentation is that the process stops when alcohol concentration reaches about 12 percent, because the alcohol that is produced kills the yeast (Nitz 1989). To produce alcohol stronger than 12 percent, the brew has to be rectified, or purified. Rectification is the process of purifying alcohol by repeatedly, or fractionally, distilling it to remove water. Alchemy, the source of modern science, was concerned in part with finding a way to transform base metals into precious metals. In their search for the most pure form of each substance, alchemists developed various processes of purification and distillation. Tradition attributes the invention of distillation to an alchemist best known as Miriam, the sister of Moses (she was later afflicted with leprosy for speaking out against Moses’s marriage to an Ethiopian), although the precise time and place of the origin of distillation is unknown (Forbes 1948). There is archaeological evidence from around 3500 to 3000 BCE of the use of extraction pots in the Mesopotamian region (Brock 1993; Levey 1960). Extraction pots were made with a double-rim trough that was percolated with holes. When the pot was heated, the steam condensed in the lid and dripped back into the pot, producing a progressively more rectified distillate. The pots were used by herbalists and perfume makers, and later adopted by alchemists, but how strong an ethanol solution might have been made in an extraction pot is not known. The Chinese distilled a beverage made from rice beer as early as 800 BC, and arrack has long been distilled in the East Indies from sugarcane, coconut flower sap, fruit, or rice (Shipman and Thomas 1991). Raymond Lully, or Ramón Lull (1235?–1315), a late thirteenth-century Spanish philosopher, wrote that distilled spirits were “An element newly revealed to man but hid from antiquity because the human race was then too young to need this beverage destined to revive the energies of modern decrepitude” (Lichine 1989, 188).
By about 50 CE, Pliny (23–79) was aware of the presence of a combustible substance in wine, which he described as “wine which can be ignited” (Monick 1968, 7), or in another translation, “There is now no wine known that ranks higher than the Falernian; it is the only one, too, among all the wines that takes fire on the application of flame” (Bostock and Riley 1855, 240). To catch fire means that the wine was at least 50 percent ethyl alcohol, as that is the minimum strength at which alcohol will burn. The wine may have been similar to brandy, which was first distilled from wine “in crook-necked pot stills” (Lichine 1989, 188) that were designed for continual reheating (and thus continual rectification) of the contents. The idea behind making brandy was to reduce the bulk of wines for shipping; once the wine arrived at its destination, the consumer could add water to reconstitute it—but the consumers preferred the stronger brandy (Lichine 1989). The word brandy comes from the Dutch word brandewijn, which means wine that burns (brandy is typically 50 percent or more ethyl alcohol).
The word distillation comes from distillare, which means “to drip off” or “to drop off” (Forbes 1948). The technique is based on the difference in the boiling points of alcohol (78.5ºC, or 173.3ºF) and water (100ºC, or 212ºF). When heated to between 78.5ºC and 100ºC, an alcoholic liquid produces a vapor that can be condensed. The condensate will have a higher alcohol concentration than the original liquid (Shipman and Thomas 1991). Distillation has a high heat requirement, so to be effective the process requires a lot of fuel (Shipman and Thomas 1991), and the earliest stills left so much water in the solution that the alcohol would not burn (hence it was less than 50 percent ethyl alcohol). Success came from two innovations. The Arabian alchemists made a stronger wine by adding salts or tartar (potassium carbonate) to absorb some of the water, based on the philosophical principle that a substance of one nature can be used to purify a substance of another nature (Leicester 1956; Partington 1989). The earliest known account of how to produce strong alcohol says to mix a pure and very strong wine with three parts salt, and then heat it (Crombie 1952; Leicester 1956). In the first century CE, Alexandrian chemists developed a better still head that more efficiently collected and cooled the distillate so it could be redistilled (Brock 1993). More sophisticated apparati followed that allowed for continuous distillations (Brock 1993). For example, better cooling systems were developed in Europe in the twelfth and thirteenth centuries (Forbes 1948). Taddeo Alderotti (1223–1303) developed a still head with a three-foot-long water-cooled tube that produced 90 percent pure alcohol (Crombie 1952; Holmyard 1957; Leicester 1956).
Hieronymus Brunschwygk (1450–ca. 1512) published the first edition of his Little Book of Distillation (Liber de arte distillandi simplicia et composita) in 1500, describing steam distillation, the use of a water bath to heat the substance, and an air-cooled conical alembic to condense it. The various editions of Brunschwygk’s book stimulated much interest in these techniques and the development of many different sorts of distilling apparati, some of which are still in use today (Leicester 1956; figure 1.1), such as the pot still and the continuous still. A pot still is an enclosed vessel, heated from underneath or by steam coils inside, with a cylindrical bulb at the top that connects to a tube that collects and cools the vapor that is produced (Shipman and Thomas 1991). A continuous still is a tall cylinder containing a series of perforated plates that collect the water-rich vapor while allowing the alcohol-rich vapor to pass through. In effect, the perforated plates function like a series of small pot stills (Shipman and Thomas 1991).
By 1606, the word rectified was being used in English in reference to its chemical meaning, “Purified or refined by renewed distillation; redistilled.” The actual quotation in which rectified first appeared in this sense in English is, “This humour . . . doth resemble the rectified animal aquavita” (Oxford English Dictionary).
Alcohol and water together do not form a true solution, but rather a binary azeotrope in which each substance keeps its own properties (e.g., the vapor pressure of alcohol and water are different, which explains why alcohol evaporates from a mixture of alcohol and water faster than the water evaporates). Distillation can increase the concentration of ethyl alcohol only to the binary azeotrope of 95.6 percent. For ethanol of greater purity, it is necessary to use chemical dehydration, which is why absolute alcohol (100 percent ethyl alcohol) is much more expensive than 95.6 percent alcohol, and why the latter has become the standard solution for museum use.
Alcohol strength is often given as a percent proof, which was first used in English in 1705, with one hundred proof defined as a concentration of eleven parts of alcohol and ten parts of water, which would permit the ignition of gunpowder (Nitz 1989). Proof is now defined as a mixture of alcohol and water with a specific gravity of 0.91984, containing 0.495 by weight or 0.5727 by volume absolute alcohol (Oxford English Dictionary), or twice the volume percent of ethanol in a sample measured at 15.56°C (Waller and Strang 1996).
Origin of the Name Alcohol
One of the curious footnotes in the history of alcohol is its many names, most of which come from alchemy. The alchemist and monk Jean de Roquetaillade (also known as Johannes de Rupescissa or John of Rupescissa, ca. 1310–1366) thought that alcohol was the supreme remedy against corruption, and named it as the fifth element, quintesseare (Leicester 1956).
The first distillation of alcohol produces aqua ardens or water that burns (Brock 1993), about 60 percent ethyl alcohol (Crombie 1952). The second distillation makes aqua vitae, or water of life, which is about 96 percent ethyl alcohol (Crombie 1952). The word whiskey is derived from a Gaelic word (uisgebeatha, or whiskybae) that means water of life (Lichine 1989). Its first recorded use in English was in a book published in 1715, which noted that “Whiskie shall put our brains in rage” (Oxford English Dictionary). In the sixteenth century, the Swiss alchemist Paracelsus (Philippus Aureolus Theophrastus Bombastus von Hohenheim, 1493–1541) derived the name of alcohol from al kohl, an Arabic word referring to a fine black powder used for eye shadow (Crosland 2004; Leicester 1956). Kohl is a paste made of black antimony sulfide—also known as stibnite, Sb2S3—in fat (Crosland 2004). In alchemy, each substance was reduced to its most pure form (Monick 1968), so a finely ground powder was considered to be an essence, or spirit, of an element, hence al kohl became alcohol in reference to the essence, or spirit of wine. The first recorded uses of the word (then spelled alcohole) in English (the first in 1615, and next in 1626) were by Roger Bacon (1214–1294) in reference to the fine powder (Oxford English Dictionary).
Glass Containers
Glass blowing originated in Syria about 1000 BCE (Derry and Williams 1960). By the seventeenth century, glass was made all over Europe, but it was very expensive. In 1615, the British navy needed more ships, so the crown issued a proclamation that gave the navy priority use of timber for shipbuilding, forbidding its use in glass furnaces (Derry and Williams 1960). Glass furnaces had to switch to coal, which burned much hotter than wood. In 1675, George Ravenscroft (1632–1683), who had learned glassmaking in Italy, developed a mixture of potash, lead oxide, and calcinated flints that could be fired in these hotter ovens to produce an inexpensive, clear flint glass with fewer bubbles (Derry and Williams 1960). This was a huge advance for fluid preservation—affordable, clear glass, and you could look through the container to see what was inside.
The Discovery of Preservation of Specimens in Ethyl Alcohol
At least one author has attributed the discovery of ethanol preservation to Roger Bacon (1214–1294), but without providing a citation for this attribution (Penrith 1971). Some authors cite the diary of Elias Ashmole (1617–1692) (e.g., Down 1989; Reid 1994) as evidence that Ashmole had in his possession a fetus preserved in alcohol as early as 1660. What the diary actually says (the entry is for October 12, 1660) is that:
This morning I showed the King the young children which Dr. Warner had preserved. The one was a male infant about 4 months, who was cut out of a woman’s belly in Covent Garden (she was dying of a consumption) and had been (now four years past) luted up in a glass, and preserved by a liquor of his preparation from putrefaccon, the flesh not so much as rumpled, but plump as it was when taken out of ye wombe. The other was 2 girls joined together by the breast and belly (which monster was borne about the king’s coming in), they were dryed and preserved with spices. (Gunther 1927, 67)
This “liquor” could mean any number of fluids—including vinegar, turpentine, or brine—that were in use for preservation at the time. The word liquor can refer to a liquid of any kind, alcoholic or nonalcoholic (e.g., liquor was used in 1604 to refer to liquid mercury, according to the Oxford English Dictionary). As late as 1890 a taxidermy text referred to temporary fluid preservation of skins by immersing them “in a barrel of brine, or what is technically called ‘liquor’—in fact, parts of alum and salt dissolved in water, in the proportion of 6 lbs. of alum and 3 lbs. of salt, sea salt if possible” (Ward 1890, 27). The word luted in Ashmole’s description refers to the sealant on the container, which was probably wax, tar, or a similarly viscous substance. Furthermore, had the fetus been preserved in alcohol for four years, it would probably have been dehydrated, not “plump.”
Several authors have made or repeated the claim that Robert Boyle (1627–1691) developed the process of preservation in alcohol, but this is not supported by evidence in the literature. Boyle was certainly interested in finding ways to preserve animal tissues, particularly human body parts, an interest that began while he was at Oxford between 1655 and 1668 (Kaplan 1993), but prior to 1662, Boyle refers to the use of brine solutions as preservatives (Reid 1994). In 1664, in the second part of Some Considerations Touching the Usefulness of Experimental Natural Philosophy, Boyle wrote:
[I]t cannot but be a great help to the Student of Anatomy to be able to preserve the parts of human Bodies, and those of other Animals, especially such Monsters as are of a very singular or instructive Fabrick, so long that he may have recourse to them at pleasure, and contemplate each of them so often and so considerately, till he have taken sufficient notice of the shape, situation, connection, etc. of the Vessel, Bone, or other part, and firmly impressed an idea of it upon his memory. (Boyle 1664, 21)
Boyle goes on to discuss various ways of preserving animal tissue by dehydration. Kaplan (1993, 51) states that “Boyle was able to develop a preservative based on turpentine that was useful in preserving small specimens,” however, this was not a fluid preservative, but rather turpentine condensed by evaporation into a gum that was then used to coat specimens. Boyle also reported on preparations in oil and in spirits of wine that he observed but did not claim to have prepared himself:
But I must not insist on theses Fancies, but rather adde, That I have known an Embrio, wherein the parts have been very perfectly delineated and distinguishable, preserved unputrified for several Yeares; and I think it still continues so, by being seasonably an artificially embalmed with Oyl (if I much misremember not) of Spikes. And I have elsewhere seen a large Embrio, which after having been preserved many Years, by means of another Liquor (whose Composition I doe as yet but guesse at) did, when I saw it, appear with such an admirable Entirenesse, Plumpnesse, and Freshnesse, as if it were but newly dead: And that which concurs to make me hope that some nobler way may yet be found out, for the preservation of dead Bodies, is that I am not convinc’d that nothing can powerfully resist Putrefaction in such Bodies, but things that are either Saline and Corrosive, or else Hot, nor that the Embalming Substances cannot be effectually applied, without ripping open the Body to be preserv’d by them. . . . And I shall anon tell You, that I have seen a Liquor, which without being at all either acid or caustic, is in some bodies far more effectual against Putrefaction, than any of the corrosive Spirits of Nitre, Vitriol, Salt, etc. and than any of the other Saline Liquors that are yet in use.” (Boyle 1664, 24–25)
Oyl of spikes refers to an essential oil made with lavender flowers. Many experiments in preservation were being carried out at this time—for example, Bolnest (1672) referred to various nonalcoholic preservatives such as salt and other chemicals in water as spirit or well rectified spirit, and a physician named Francis Hume was experimenting with the preservation of fish and beef in limewater in the mid-1700s—the fish remained in good condition for seven weeks, the beef did not (Clephane 1753).
Some authors have claimed that Boyle’s description of preserving avian embryos (Boyle 1666) is the first account of fluid preservation, but there are older published accounts of preservation in alcohol. Yet another author remarked, without providing a citation for the evidence, that:
It will thus be realised what an incalculable advance was made in museum technique by Robert Boyle’s experiment, carried out on William Croune’s suggestion, of preserving parts of, or even whole, animals in spirit. Boyle’s specimens of “a linnet and a little snake, preserved already four months, entrails and all, without any change in colour, in some spirit of wine,” placed in the repository of the Royal Society at Gresham College in 1663, were still in existence a hundred and fifty years later. (Dobson 1970, xii)
The role of “William Croune” will be discussed next. Dobson was quoting the Proceedings of the Royal Society for January 20, 1664. The full quotation is as follows:
[Mr. Boyle] presented the society with a linnet and a little snake, preserved already four months, entrails and all, without any change of the colour, in some spirit of wine made after a peculiar manner. Both the glasses, wherein they were kept, were ordered to be sealed up with wax, and put into the repository.
Dr. CLARKE mentioned, that there was an intention of preserving the whole body of a man with spirit of wine in a vessel well glased; suggesting the usefulness of this method of preserving, that by this means there might be had in readiness for occasions an eye, hand, muscles, larynx, &c.
Dr. MERRET affirmed, that he had preserved the very entrails of a cat for twelve years past, though they were somewhat shrunk.
Mr. BOYLE observed, that he had a liquor compounded of spirit of wine and a little oil of turpentine, whereby not only the bodies of animals or the parts thereof might be preserved, but also it might be known what it is that comes away; which being such, that it will not mingle with the oil, falls to the bottom, and is found there.
He offered to preserve a hand and a larynx. (Birch 1968, 374)
In fact, the linnet and the snake referred to were preserved in 1664 (Cole 1944), as recorded in Musaeum Regalis Societatis, or a Catalogue and Description of the Natural and Artificial Rarities Belonging to the Royal Society and Preserved at Gresham Colledge, published by Nehemiah Grew (1641–1712) in 1681. In this detailed catalog, Grew (1681, 48) describes “A snake preserved in Spirit of Wine”; “A young LINET which being first embowel’d, hath been preserved found and entire, in rectified Spirit of Wine, for the space of 17 years. Given by the Honourable Mr. Boyl. Who, so far as I know, was the first that made trial of preserving Animals this way. An Experiment of much use. As for the preserving of all sorts of Worms, Caterpillars, and other soft-Insects in their natural bulk and shape, which otherwise shrink up, so as nothing can be observed of their parts after they are dead. So also to keep the Guts, or other soft parts of Animals, fit for often repeated Inspections. And had the Kings or Physitians of Egypt thought on’t, in my Opinion, it had been a much better way of making an everlasting Mummy” (Grew 1681, 58); and “A young CHICKEN emboweled and put into rectified Oil of Turpentine, at the same time, with the Linet, and preserved found; Only there is a little sediment at the bottom of the Glass” (Grew 1681, 58). As the specimens had been in the collection for 17 years, this would mean they were preserved in 1664 or shortly before.
The first recorded mention of the use of alcohol for fluid preservation was on June 4, 1662. A physician, William Croone (1633–1684) (his name was also spelled Croune), appeared before the Royal Society of London and “produced two embryos of puppy-dogs, which he had kept eight days, and were put in spirit in a glass-vial sealed hermetically” (Birch 1968; Cole 1944). Croone was born in London and received his M.D. degree in 1662; he was mentioned several times in the diary of Samuel Pepys (Payne, Wilson, and Hartley 1960). Croone believed that muscular motions were produced by “vital spirits” (an idea from Decartes) that flowed along the nerves and mixed with the spirit of the blood (Debus 1968). After Croone’s presentation of the preserved embryos to the society, the Transactions report that “Mr. Boyle promised to make the like experiment in rabbets.” The next mention of the technique was when another member brought in an “abortive human foetus, kept in spirit well rectified.” In 1664, Boyle brought to the Royal Society the specimens of a linnet and snake which he had preserved in spirit of wine four months previously (Cole 1944), and in 1665, the society records noted that Boyle showed “the head of a colt” which he “Caused . . . to be put into a Vessel, and covered with Spirit of Wine, thereby chiefly intending, to give good example, together with a proof, that by the help of the said Spirit . . . the parts of Animals, and even Monsters, may in Summer it self be preserved long enough, to afford Anatomists the opportunity of examining them” (Boyle 1665).
Although Boyle took an interest in the use of alcohol as a preservative, his speculations on the topic in Some Considerations Touching the Usefulness of Experimental Natural Philosophy were clearly based on the work of others:
Nor were it amisse that diligent Tryal were made what use might be made of Spirit of Wine, for the preservation of a humane Body. For this Liquor being very limpid, and not greasie, leaves a clear prospect of the Bodies immers’d in it, and though it doe not fret them, as Brine, and other sharp things, commonly imploy’d to preserve flesh, are wont to do, yet it hath a notable Balsamic faculty, and powerfully resists Putrefaction, not onely in living Bodies (in which, though but outwardly applied, it hath been found of late one of the potentest Remedies against Gangrenes) but also in dead ones. And I remember that I have sometimes preserv’d in it some very soft parts of a Body for many Moneths) and perhaps I might had done it for divers Years, had I had opportunity) without finding that the consistence or shape was lost, much lesse, that they were either putrified or dried up. (Boyle 1664, 25–26)
Nevertheless, Boyle later experimented with fluid preservation, and based on his experience, recommended changing the alcohol solution after the initial preservation of the specimen, redistilling the preservative when it became diluted or discolored, and testing the strength of ethyl alcohol by soaking a strip of paper or cloth in the solution and then trying to light it (Boas 1958).
The idea of fluid preservation caught on quickly, but the use of the technique was limited by the expense of the alcohol and the glass containers. As late as 1813, one anatomical preparation manual lamented that, “Preparations of almost every part are occasionally kept in spirits, unless their size renders it impracticable, more especially diseased parts; as by this mode they undergo less change of appearance than by any other method of preservation, and consequently give the best idea of the natural or diseased appearance; but the expensiveness of the glass and spirits is a great inducement to the making of so many dry preparations” (Pole 1813, 163). The preservation methods recommended were not always very refined. For example, in 1748, René-Antoine Ferchault de Réaumur (1683–1757) stated that, “There is no great Skill required for putting one or several [specimens] into a Vessel full of Spirit of Wine, or very strong Brandy. It has been usual for a long time to make use of those Liquors with Success for preserving the Flesh of dead Animals” (Réaumur 1748, 307). There are records of the preservation of a human fetus in 1665 by T. Coxe, of insects in alcohol by 1670 by Jan Swammerdam (1637–1680), and the body of a child being kept for several years in alcohol, reported in 1678 (Cole 1944). The most distinctive and best preserved specimens from this time were those prepared in Holland by Frederik Ruysch (1638–1731), a surgeon and anatomist in Amsterdam. Ruysch distilled his own alcohol from barley, producing about 67 percent ethanol from this process (Singer 1921). Although most of Ruysch’s techniques were closely guarded secrets, it is thought that some of his preservative solutions included black pepper, cardamom, and cloves mixed with the alcohol (Cole 1944). Ruysch perfected the methods of vascular injection that revolutionized the quality of fluid preserved specimens by providing a better means of distributing preservative in the tissues (Singer 1921). Ruysch was able to preserve soft brain tissue by a combination of injection of the veins and arteries with wax and vermilion and the use of his own alcohol recipe, and made a few brief mentions of his techniques in the catalog of his collection, his Thesaurus Anatomicus (published between 1727 and 1744) and in letters to colleagues (Cole 1921; Gere 2003). Ruysch sold a collection of anatomical preparations to Peter the Great (1682–1725) for his Kunstkamera in 1717 (Peter the Great had first seen the Ruysch collection in 1697 when he visited Amsterdam). Many of the specimens survived war and other afflictions and can still be viewed at the Anthropological and Ethnographic Museum in St. Petersburg, Russia (Humphries 2003).
One very famous collector of the era was the Englishman James Petiver (ca. 1663–1718), who solicited specimens from many travelers around the world. He published a sheet of instructions called “Brief Directions for the Easie Making and Preserving Collections of all Natural Curiosities for James Petiver Fellow of the Royal Society of London” that was widely distributed to travelers and sailors (Stearns 1953, 363). Petiver advised that “All small Animals, as Beasts, Birds, Fishes, Serpents, Lizards, and other Fleshy Bodies capable of corruption, are certainly preserved in Rack, Rum, Brandy, or any other Spirits; but when these are not easily to be had, a strong Pickle, or Brine of Seawater may serve” (Stearns 1953, 363). Rack is a shortened form of arrack, an alcoholic beverage distilled from either the juice of coconut palm or a mash of rice and molasses. Even with these recommendations, some of Petiver’s collectors improvised fluid preservatives of their own. John Lawson, collecting in North Carolina in 1710, wrote to Petiver to explain that his “bottles are too small & too narrow mouths for some large snakes, etc. I can no ways preserve snakes, Lizards & small birds but in Spirits. I had a curious liquor of Mr. Fettiplace Bellers that preserved bird-skins very well it is all gone I have made a liquor of my own which does it reasonably well wch. is aloes, myrrh, allom & tobacco steept in rum. I take his to be something of that nature but it gives them a shining varnish wch. mine does not pray get his recipe & speak to him to send a quantity” (Lefler 1967, 270). When the artist and naturalist Maria Sybilla Merian (1647–1717) returned to Europe from a two-year stay in Surinam, she wrote to a physician to explain that:
When I was in that country I painted and described the larvae and caterpillars as well as the kind of food and habits; but everything I did not need to paint [there] I brought with me, such as the butterflies and beetles and everything which I could steep in brandy and everything which I could press I am now painting the same way as I did when I was in Germany, but everything on vellum in large format with the plants and creatures life size. (Owens 2007, 148)
A good number of the published recipes for fluid preservatives from the earliest days onward call for additives to the alcohol, particularly alum and mercuric chloride, but including a wide variety of acids and salts, and other substances (tables 1 and 2). The additives were assumed to make the alcohol a better preservative. At the time, it was difficult to assess the strength of alcohol (other than seeing if it would burn, which indicated a strength of about 50 percent or greater), so many of the additives were probably necessary to compensate for low concentrations of ethanol that were available. In addition, many of the additives had been used as preservatives before the discovery of the preservative properties of ethanol, so it was natural to combine them in an effort to produce a better preserving fluid.
In 1753, Carl Linnaeus (1707–1778) published Instructo musei rerum naturalium, which included a number of preservation techniques (such as attaching dried fish to paper sheets in a manner similar to how plants are mounted in herbaria), including the recommendation to add sugar to alcohol for preserving lower vertebrates (Holm 1957). Linnaeus also provided a detailed account of how to seal glass cylinders of specimens by using cork stoppers sealed with tragacanth (a gum extracted from the legume Astragalus gummifer), a sealant so successful that several of the jars sealed by Linnaeus are still extant (Holm 1957).
In a description of his travels in Guiana, published in 1769, Edward Bancroft (1744–1821) described some techniques then used for fluid preservation, referring to a technique “since published in one of the monthly Magazines; and the author, if I mistake not, thought it an important discovery, which, it seems, he obtained in Paris, tho’ not without great difficulty” (Bancroft 1769, 184). Bancroft is most probably referring either to a publication by Réaumur (1748) or a review of it (Bancroft refers to Réaumur by name a few pages later). It is interesting to note that Bancroft recommended the use of alcohol for both specimens that would later be dried (birds) and those that will remain in fluid (snakes):
The method of doing this in Guiana, is to put the Bird, which is to be preserved, in a vessel, and cover him with High Wines, or the first Running of the Distillation of Rum. In this Spirit he is suffered to remain for twenty-four or forty-eight hours, or longer, according to his size, til it has penetrated thro’ every part of the body. When this is done, the Bird is taken out, and his feathers, which are no ways changed by this immersion, are placed smooth and regular. He is then put into a machine, made for the purpose, among a number of others, and its head, feet, wings, tail &c. are placed exactly agreeable to life. In this position they are all placed in an oven, very moderately heated, where they are slowly dried, and will ever after retain their natural position, without danger of putrefaction. This method might perhaps in England be deemed expensive, as the great duty on Spirits has raised their price to an enormous height; but in a country where Rum is sold for ten pence sterling per gallon, the case is far different. (Bancroft 1769, 184–185)
The method which I use in preserving these Animals, may perhaps not be unworthy of a communication. When the Snake is killed, it must first be washed clean, and freed from all filth and nastiness; then it is to be put into a glass of a proper size, the tail first, and afterwards the rest of the body, winding it in spiral ascending circles, and disposing the back, which is always the most beautiful, outwardly. A thread, connected to a small glass bead, is, by the help of a needle, to be passed thro’ the upper jaw from within outwardly, and then thro’ the cork of the bottle where it must be fastened: by this means the head will be drawn into a natural posture, and the mouth kept open by the bead, whereby the teeth, &c. will be discovered: the glass is then to be filled with rum, and the cork sealed down, to prevent its exhalation. A label, containing the name and properties of the Snake, is then to be affixed to the wax over the cork; and in this manner the Snake will make a beautiful appearance, and may be thus preserved a great number of years; nor will the spirits impair or change the lustre of its colours.” (Bancroft 1769, 218–220)
Not everyone was convinced that fluid preservation was an acceptable means of preserving specimens. Tessor Samuel Kuckahn (misspelled as T. S. Kuckhan in the Philosophical Transactions), in describing various means of preserving birds, stated that:
A second method of preserving birds is, by immerging them in spirits, and if the barely keeping the carcase of birds from putrefaction is all that is required, I must own this method is an effectual one, and congratulate the naturalists on the facility with which they may now procure foreign birds. We have nothing to do but send by sailors bound to different parts of the world, a few kegs of spirits, and we shall be sure of birds enough preserved in this manner; but then what becomes of their proportions, attitudes, graces, and in short, of every thing that gives them life and motion? (Kuckhan 1771, 304–305)
Two such birds collected by the naturalists on one of Captain Cook’s voyages and given to the Hunterian collection in 1792 are among the oldest extant fluid-preserved bird specimens. They were examined and dissected when rediscovered, and were described as being in “remarkably good condition” after 190 years of preservation (Burton 1969, 389).
By the early 1800s, the practice of preservation in spirit of wine was well enough known for many people to have an opinion about it, including those who had never done it, which led to the criticism directed at the surgeon who preserved the body of Admiral Nelson. After the Battle of Trafalgar in October 1805, the body of Admiral Lord Nelson (1758–1805) was preserved in fluid for the long trip back to England. The ship’s surgeon, William Beatty (1773–1842), later published an account of the event, explaining the procedure—Nelson’s body, clad only in a shirt, was put in a large cask that was then filled with brandy and lashed to the deck. The cask had two apertures, one at the bottom for drawing off brandy and another at the top for adding fresh brandy as needed. As it happened,
On the 24th there was a disengagement of air from the Body to such a degree, that the sentinel became alarmed on seeing the head of the cask raised: he therefore applied to the Officers, who were under the necessity of having the cask spiled to give the air a discharge. After this, no considerable collection of air took place. The spirit was drawn off once, and the cask filled again, before the arrival of the Victory at Gibraltar (on the 28th of October): where spirit of wine was procured; and the cask, shewing a deficit produced by the Body’s absorbing a considerable quantity of the brandy, was then filled up with it. . . . When the Victory had proceeded some weeks on her voyage, adverse winds and tempestuous weather having prolonged the passage much beyond the period that is generally expected, it was thought proper to draw off the spirit from the cask containing Lord NELSON’S Body, and renew it; and this was done twice. On these occasions brandy was used in the proportion of two-thirds to one of spirit of wine. (Beatty 1807, 63–64)
Once the body arrived in England, Beatty was criticized in the British press for not preserving the body in rum, which was commonly believed to be a better fluid preservative than brandy. In his defense, Beatty argued that:
Brandy was recommended by the Surgeon in preference to rum, of which spirit also there was plenty on board. The circumstance is here noticed, because a very general but erroneous opinion was found to prevail on the Victory’s arrival in England, that rum preserves the dead body from decay much longer and more perfectly than any other spirit, and ought therefore to have been used: but the fact is quite the reverse, for there are several kinds of spirit much better for that purpose than rum: and as their appropriateness in this respect arises from their degree of strength, on which alone their antiseptic quality depends, brandy is superior. Spirit of wine, however, is certainly by far the best, when it can be procured. (Beatty 1807, 62)
Early Instructions for Preserving Specimens in Fluids
Initially, fluid preservation was a laboratory procedure, but quickly became a means for preservation of specimens in the field as well. By the early 1800s the published recommendations for alcohol-based preserving fluids usually included additives (table 2). Most of the people who were preserving specimens in the field were not naturalists but sailors or other travelers who were acquiring specimens to sell to collectors in Europe—for example, Albertus Seba (1665–1736) is not known to have done any fieldwork himself, but purchased his specimens from sailors at the docks or from commercial dealers, then rebottled his specimens for his museum. Throughout the 1800s the published instructions for fluid preservation tended to either specify just beverage alcohol (easy to obtain and use) or called for spirits of wine with various chemical additives.
The years following Croone’s 1662 demonstration were a time of great experimentation with fluid preservation, with numerous individuals making recommendations for their own particular concoctions. In 1688, Blanckaert (in Tractatus de Balsamatoione) recommended three different liquors—salt water with alum, oil of turpentine, and rectified spirit of wine with a little sal ammoniac (ammonium chloride) (Edwards and Edwards 1959). As confidence in the preservative powers of alcohol-based liquids grew, people were willing to invest more in the system. In addition to reporting the linnet that had been preserved for seventeen years (discussed earlier), Grew also described a human fetus: “The skin hath been kept white and smooth for so long a time scil: above 15 years, by being included with rectified Spirit of Wine in a Cylindrical Glass to the middle of which the Foetus is poised, by means of a bubble of an inch diameter, the Neck whereof is fastened to the Anus of the Foetus by a wire” (quoted in Edwards and Edwards 1959, 12).
Specific instructions for field preservation of specimens were not long in coming. In 1691, John Woodward published Brief Instructions for Making Observations which recommended drying specimens “unless you rather think fit to put some of the more rare, curious, and tender, into small Jars, filled with Rum, Brandy, or Spirit of Wine, which will keep them extremely well” (Edwards and Edwards 1959, 12). While writing a catalog of the museum in the Jardin des Plantes, Daubenton mentioned that although spirit of wine was used because it was plentiful, all fermented liquors seemed to be equally effective, certainly better than salt or alum, and he reported success with rum and observed that specimens sent from the Americas in undistilled rum were often yellowed. Daubenton claimed to know Ruysch’s secret formula (mix 1 oz. 6 dr black pepper, 1/2 oz. small cardamomium seeds, and 1/2 oz. of cloves in 12 lbs. of spirit of wine; add 2 oz. of camphor, then distill the fluid down to 11 lbs. 3 oz. and dilute before use) (Edwards and Edwards 1959).
Most specimens were preserved in fluid in the field simply by dropping them—alive or dead—into a wooden cask or keg (or later into metal containers) of some form of alcohol. Glass vessels were rarely taken into the field for several reasons—glass was expensive and fragile; it was difficult to get an effective seal on glass containers (see the following discussion); and most collecting was done by individuals for whom collecting was not a major occupation, thus they did not carry much preserving equipment with them. Although there are some accounts of some glass vials and cylinders being used for field preparation, until the mid-1800s jars had to be sealed with bladders and disks made of wood, cork, or tin. After John Mason invented the screw-on zinc jar lid for threaded jars in 1858, glass containers became much more commonly used in the field.
In reference to containers for specimens, in 1748, Réaumur wrote that:
This vessel may be a jar of glass, if it is only intended for receiving small birds; one may contain a great number of them, which you may put in at different times, accordingly as you get them, till it is quite full. Wooden barrels however are preferable to jars, as they are not liable to break in long journeys; there are to be had very small ones for smaller birds, and some large enough for others of the tallest size. The barrel is to have a hole large enough for passing the birds through: this hole can be no other than the bung widened, it will even be better placed in one of the heads. (Réaumur 1748, 309).
Réaumur went on to say that once bird specimens had been soaking in alcohol for eight days to six weeks (depending on size), the specimens could be removed from the fluid and packed in a box in chaff or straw for shipment. Réaumur had previously (1746) described two methods for sealing jars of specimens. If the jar had a stopper, mercury or thickened nut oil could be put into the alcohol and the container inverted to allow the additive to settle around the stopper. Réaumur also mentioned receiving a jar with a lid that formed a gutter around the neck for the application of mercury or oil. If the container did not have a stopper, Réaumur recommended a layer of thickened nut oil spread under the bladder (Edwards and Edwards 1959). Dumberton suggested sealing stoppered jars with tallow or a mastic (Edwards and Edwards 1959). Nicola (1771) recommended tying on the bladder, covering it with a layer of putty, then turning the container upside-down and setting it into a cup of melted tallow, or coating the neck of the container with oil and using an oil-soaked cork along with putty and a bladder (Edwards and Edwards 1959). In 1607, Sir Hugh Plat devised a system for the British navy for sealing jars of preserved food with a layer of olive oil (Shephard 2000). A description of how to preserve specimens written in 1773 recommended putting specimens in a cask of rum (or any other spirits) for preservation and shipment (Walker 1811).
A well-known guide for field collection and preservation first published in 1817 (The Naturalist’s Pocket Book) recommended that small specimens of quadrupeds could be preserved in a mixture of alcohol and alum:
The solution of alum should be made by pouring one quart of boiling water on eight ounces of alum and when cool, the water should be poured off, as some water will not hold that quantity in solution; and if a larger quantity be dissolved at any one time than is required, the water may be evaporated either over a fire, or by placing the solution within the influence of the sun, and the alum will be deposited in crystals, which only require being burnt over a common fire to be fit for using again. (Graves 1817, 54)
Graves recommended preparing burnt alum “by burning common alum over a fire till it looses its transparency” (1817, 55–56). His specific instructions for preserving large turtle and tortoise specimens included opening the skin at the throat, removing as many internal organs and as much muscle mass as possible, then submerging the specimen “in a strong solution of burnt Allum for a few hours, after which, it should be removed into a jar, and completely covered with the same kind of preparation as directed for preserving Quadrupeds in spirits, the feet and tail may also be preserved in the same way” (Graves 1817, 152–153). Smaller specimens “may be preserved entire, for these it will be proper to mix one half of pure spirit, with an equal quantity of Allum; the latter to be made by pouring three pints of boiling water over one pound of burnt Allum, which shou’d be suffered to cool previous to mixing it with the spirit. Frogs, the smaller kinds of lizards and Serpents, are best preserved in these last-mentioned preparations, as likewise the eggs of such as are not covered with a hard shell” (Graves 1817, 153). Fishes may be preserved “as for lizards” (Graves 1817, 184) and “vermes” and shell-less invertebrates in a mixture of one-third spirits and two-thirds burnt alum. Concerning quadrupeds in general, Graves wrote that:
As it may be more convenient, at the time of procuring many of the smaller species of Quadrupeds, to preserve them entire, till a more convenient opportunity offers for stuffing them, they can be safely put into glass or earthen jars, or small casks filled one third spirit of wine, arrack, rum, or other spirit, and two thirds of a strong solution of burnt alum, care should be taken not to use, if avoidable, coloured spirit of any kind, as it frequently happens that when coloured, it will leave a stain on the lighter parts of the skin or fur, that cannot be removed. (Graves 1817, 54)
Instructions for field preservation extracted from a French publication and reprinted in Edinburgh in 1828 (Bory de Saint-Vincent 1828) recommend a variety of fluids, including brine, vinegar, oil, and acid solutions, with a comment that while alcohol is the most efficient fluid preservative, it causes alterations of colors and hardens tissues. The author notes that “It will be kept in mind, that alcohol becomes milky when diluted with common instead of distilled water” and recommends diluting alcohol to 16°–22° Baumé for preservation, and adding camphor (the Baumé scale is an expression of specific gravity such that 16°–22° Baumé = 0.959 to 0.921 specific gravity, or about 59–47 percent ethyl alcohol in water). Bory de Saint-Vincent recommended cleaning specimens before preservation, and cautioned that square glass bottles are a better shape for traveling than round bottles as they are easier to pack. Fishes should be packed in small casks with iron hoops, with an opening in one end that is six inches in diameter; specimens should be wrapped in cloth and have a wooden tag attached before they are inserted into the cask. When the cask is full, cotton or flax should be stuffed in to prevent the specimens from moving, then the cask should be sealed. In warm climates, Bory de Saint-Vincent recommended suspending the specimens in the preservative by cork floats to allow the preservative to penetrate from all sides. Incisions should be made in the abdomens of large animals. Vessels containing specimens should be sealed by soaking a cork in a mixture of three parts wax and one part tallow, then covered with a mastic of four parts pitch, one part sulfur, and one-half part tallow, melted together. Alternatively, a round glass plate may be placed over the container, then covered with a piece of oiled parchment, then lead, then parchment soaked in oil colored with lampblack and tied on with a cord (a cork stopper may be substituted for the glass plate). An alternative sealant can be made by melting common resin and yellow wax together, then adding red ochre a little at a time before boiling for seven or eight minutes, then adding turpentine; this solution is to be brushed over the cork and covered with a piece of linen.
A manual on specimen preservation written in 1831 stated that reptile and fish specimens should be “transported in spirit; we know of no better method than that proposed by M. Dufresne:—Wrap the fish in a cloth, and sew him up; fill a cask two-thirds with any sort of spirit, choosing that which is not too highly coloured,—its strength should be equal to 14 or 15 degrees of Baumé’s aerometer: at the bottom of the cask put the largest fish, and decrease in size till you have filled it; the cask should be headed and hooped tight, and done over with pitch” (Anon. 1831, 79–80).
In 1852 Spencer Fullerton Baird (1823–1887) instructed those interested in preparing specimens for the U.S. National Museum that “The collector should have a small keg, jar, tin box, or other suitable vessel, partially filled with liquor, into which specimens may be thrown as collected. They should be alive, or as near it as possible when this is done, as besides the speedy and little painful death, the animal will be more apt to keep sound” (Baird 1852, 13). A few years later Templeton Hoffman Bean (1846–1916) noted that “Oak kegs, holding about 10 gallons each and provided with iron hoops, are capital containers for large fishes and they will stand the wear and tear of railway travel better than most other receptacles” (Bean 1881, 237).
In 1831, Leonhard Hess Stejneger (1851–1943) published directions for collecting and preserving specimens that recommended a one-gallon copper collecting can and a chest of copper tanks to fill with alcohol to preserve specimens in the field and then ship them home. In a review of pamphlets issued to collectors by the American Museum of Natural History, Myers (2000) reported that the earliest version he found (from 1919) recommended shipping specimens in metal cans (five-gallon square kerosene cans); later versions still recommended cans in addition to jars. For example, “For shipping or transportation, after the specimens have been in preservative for two weeks, the packages should be removed from the liquid, packed snugly in a can . . . the cans should then be sealed with solder” (Myers 2000, figure 43). The 1921 version of the Handbook of Instructions for Collectors issued in several editions by the British Museum (Natural History) in London stated that:
The collector should provide himself with the best and strongest alcohol procurable. This can afterwards be diluted with water or with weaker spirit, until it is reduced to the degree of strength required in each case. As difficulty is often experienced in obtaining spirit while traveling, the collector is advised to take a sufficient supply with him. If an excise permit can be obtained, “industrial methylated spirit” may be recommended on account of its greater cheapness; but specimens do not keep so well in this liquid as in pure spirit, and it should not be used for the preservation of particularly valuable specimens, or of such as are likely to form the subject of anatomical investigation, in cases where pure spirit can be employed. In default of spirit the collector may use arrack, brandy, rum, or any other spirituous liquid which he can procure, provided it possesses the requisite strength. Any spirit which takes fire immediately on the application of a light, without having been previously warmed, is strong enough to be used for the preservation of animals. Spirit in which specimens are finally packed for transmission should contain 74–80 per cent. by volume of alcohol, or about 30–40° over Proof.
It is sometimes found advisable to mix an emetic, crushed colocynths or other disagreeable ingredient with the spirit, in order to deter pilferers from drinking it. (Anon. 1921, 46–47)
The same publication later states that formaldehyde is not recommended as a preservative for amphibians, reptiles, or fish with soft and delicate skin (Anon. 1921).
Later Instructions for Preserving Specimens in Fluids
Although quite a number of publications exist that describe various ways to preserve specimens in fluid (table 1), there are few detailed accounts of how these practices were actually carried out in the field by collectors. Joseph Richard Slevin (1881–1957) of the California Academy of Sciences wrote that “The specimens, having been thoroughly hardened and preserved, must be packed in jars, cans, or tanks, for storage or shipment” (Slevin 1927, 242). Similarly, a British Museum (Natural History) pamphlet of instructions for collectors recommended glass jars as well as “metal tanks, fitted with screw covers and encased in boxes” as being “more economical of space than boxes of jars and are stronger.” The pamphlet further advises that “Well-galvinised milk cans of 3 to 10 gallons capacity are perhaps the most convenient of all field-containers” (Anon. 1953, 6). Improvements in the construction of metal containers is reflected in a later statement in the same publication that “Wooden casks are unsuitable, especially in hot countries, for the transport of specimens in spirit; they should not be employed except in cases of necessity or for packing large dry or salted specimens” (Anon. 1953, 10).
Clifford Hillhouse Pope (1899–1974) collected in China between 1921 and 1926 for the American Museum of Natural History Central Asiatic Expeditions (Adler 1989). In 1940, Pope published a popular account of his fieldwork, including a description of his working habits, writing that “My own ambition was to bring back nothing but flawless specimens” (Pope 1940, 184), while lamenting that “The preparation of specimens in the field required training and experience, although it was not highly skilled work” (Pope 1940, 188). To accomplish his goal, Pope hired one Chinese assistant to skin mammals and another to serve as his “injector” of fluid-preserved specimens. Pope provided the following detailed description of how his specimens were prepared:
Only the largest reptiles were skinned: monitor lizards, large pythons, and other snakes more than five feet long. A snake was excoriated by making a short incision along the throat, severing the neck inside, and peeling the skin back to the tail, which, like the head, was left whole and attached to the skin. The body was discarded. Snakes not prepared in this way were preserved whole by injections of formaldehyde into the body cavity and tail and under the skin along each side. Very small individuals did not require the subcutaneous injections. Lizards in general were treated like snakes of medium or small size. All elongated reptiles were fitted into their containers immediately after preservation and before formaldehyde had made them hard and stiff.
Turtles were easily preserved by inserting the injection needle into the body through one of the exposed fleshy parts, but of all reptiles no kind is really so hard to pack. Place turtles as you will, much space remains vacant. Relatively little is known about these creatures because most collectors simplify transportation by saving only their dried shells. Snakes, on the other hand, can be packed like so much rope, the small specimens filling the space inside the big ones.
Frogs and salamanders were easily preserved because they have moist skin in life which, after death, is readily penetrated by formaldehyde. Only the large frogs had to be injected although I found it wise to see that a little preservative entered the body cavities of those medium in size. Fish more than a few inches long made better specimens when injected as thoroughly as amphibians, which they resemble in having permeable skin.
The chief implement used in reptile and amphibian preparation was a large ear syringe with needles of all sizes. Rubber gloves are indispensible for many workers because formaldehyde hardens and cracks the skin, producing in some an almost incurable irritation of the skin. The worst pain that I suffered was not by some dread Chinese malady, but by lack of caution in the handling of formaldehyde. No bad effects may be felt from a single day’s work with this preservative; after the third or fourth successive one, however, the skin cracks appear into which the liquid flows, causing sharp pain. The scalpels and scissors used on the mammals also served in the preparation of the cold-blooded animals. . . .
The “wet” reptiles, amphibians, and fishes were first carefully packed in five-gallon Standard Oil tins. These were nailed in wooden boxes by twos after the tops had been soldered in place to keep the surplus formaldehyde from leaking out. (Pope 1940, 190–192)
Fluid-Preserved Collections
Preserving the specimens in fluid was one thing, maintaining them was something else. Thomas Pole (1753–1829) noted in 1790 that “It is found to be attended with no small difficulty, to enclose wet preparations in glasses, so as to prevent effectually the evaporation of the spirits, which occasions very considerable trouble, and no small expense to keep a large anatomical collection in good order” (Pole 1790, 259). As noted earlier, there were many variations in sealing glass cylinders, but the basic technique was to cover the mouth of the jar with one or two pig or sheep bladders, which were then varnished and heavily coated with wax, lead, glaziers putty, or other substances, including bitumen and various jar cements (figure 1.2). Sometimes the bladders were put over a cork, glass plate, waxed paper, or piece of lead or tin foil. If done right, it was a fairly effective seal, except for the fact that it had to be destroyed to retrieve the specimen. After a discussion of commonly used techniques to bladder glass cylinders, Parsons’s (1831) recommendation was:
to cover the edge or rim of the glass, with fine soft Glazier’s putty; then cover the mouth completely with a piece of flat common window glass, cut to the exact circumference of the rim of the vessel it is designed to cover; the putty should be laid on with great smoothness, so as to guard against any air-holes; the surfaces of the glass to come in contact with the putty, should be previously rubbed with a little boiled linseed oil, the glass cover should then be carefully applied, over this may be stretched a bladder or two, and bound as before described, covering the bulge of the vessel: when perfectly dry, the edge of the bladder round the bulge, should be cut even with a knife, and the bladder covered with a black varnish, to make it more secure, defend it from wet, and give it a neater appearance; or the glass vessels may be made with covers, fitted on with putty. (Parsons 1831, 122)
Parsons reported that he made his varnish by mixing lamp black with copel (oil varnish). However, acid-based preservatives will decompose the putty and the oil of turpentine will soften the putty, so instead “A lute may in such cases be made of finely powdered, and dry brick dust, four parts; common rosin, three parts; yellow wax with sufficient spirits of turpentine to mix it, one part” (Parsons 1831, 123). Other suggested sealants were made of gum mastic; chalk and egg white; or a mixture of common resin, red ochre, yellow wax, and oil of turpentine.
Figure 1.2. Glass jar sealed with a bladder (note rupture in bladder).
The traditional jar sealing method in the Netherlands was to use a cork stopper or “chiselled plate of schist,” covered by a pig or sheep bladder, varnished, and then coated with a wax, such as beeswax, carnauba wax, or a mixture of colophonium and chalkpowder (van Dam 1997).
If done right, a bladder closure could be very effective—some of the fluid-preserved specimens featured in Seba’s Thesaurus (1734) are still extant, having been carefully preserved in their original jars (sealed with distinctive red wax) in the collection of Lidth de Jeude and acquired in 1867 by the British Museum (Thomas 1892). On the other hand, many specimens were lost due to failures of the containers or closures, particularly during the long and difficult journey from the field to the museum. For example, a student of Linnaeus, Peter Forsskal (1732–1763), collected fish in alcohol as naturalist on a Danish expedition to the Red Sea from 1761 to 1767. Forsskal and three other expedition members died on the trip. Unfortunately, there was a delay of two years before Forsskal’s fishes could be shipped back to Denmark, and by then, all the specimens had been destroyed because the alcohol had evaporated (Davis 1993). The explorer and naturalist Alexander von Humboldt (1769–1859), recounting his 1799–1804 trip to the New World, remarked that “Sad experience taught us but too late, that from the sultry humidity of the climate, and the frequent falls of the beasts of burden, we could preserve neither the skins of animals hastily prepared, nor the fishes and reptiles placed in phials filled with alcohol” (von Humboldt 1889). Similarly, Manuel Almargo y Vega (1834–1895), a member of the 1864–1865 Comisión Científica del Pacífico, wrote in his diary that “Bien es verdad que la adquisición de los objetos de historia natural era sumamente difícil a causa de los escabroso del suelo y de la abundancia de las lluvias; pero si la adquisición era difícil, la conservación lo era más aún, pues la grande humedad que había nos obligada a inventar medios artificiales para secar nuestras plantas y aves disecadas” (It is true that the acquisition of objects of natural history was extremely difficult because of the rocky soil and the abundance of rainfall; but if the acquisition was difficult, the conservation was even more, as high humidity forced us to invent artificial means to dry our plants and stuffed birds) (Cabodevilla 1998, 103).
In his 1849 text on embalming, Jean Nicolas Gannal (1791–1852) summed up the available fluid preservatives by writing that:
Alcoholic liquors are most generally used for the preservation of animal substances, if they are more costly, they are liable to fewer objections. Brandy, rum, tafea, are colored by a resinous substance which clouds their transparency, and which is liable to be deposited. The alcohol of cherries, of grain, of cider, or of wine, is preferred at present, which can be procured well rectified with distilled water, so as to obtain alcohol very limpid, marking from 22° to 30° of Baumè’s areometre. (Gannal and Harlan 1840, 167). [22° to 30° Baumè is equivalent to 92 percent to 88 percent ethyl alcohol in water]
Other Fluid Preservatives
As mentioned previously, ethyl alcohol was not the only fluid preservative in use—brine and vinegar were quite common. In 1663, one year after Croone showed the first fluid-preserved dog embryos before the Royal Society, Robert Hooke (1635–1703) demonstrated “leeches in vinegar” to the same group (Huxley 2007, 101). Around 1753, in his Instructio musei rerum naturalium, Linnaeus recommended adding some sugar to the alcohol for the preservation of lower vertebrates (Holm 1957). In 1749, the Paris museum was still preserving specimens in rum (Cole 1944). In his 1840 book, Gannal suggested as alternatives to alcohol (which he considered to be very expensive) a solution of water (2 lbs.), alcohol (1 lb.), and aluminum sulfate (6 oz.); a solution proposed by the English naturalist George Graves consisting of alum (8 oz.), common water (1 lb.) and alcohol (1/2 lb.); or a solution promoted by Abbe Manesse of alum (1 lb.), nitre (1 lb.), sea salt (1 lb.), common water (4 lb.), and alcohol (1 lb.), with the caution that “all these liquors are inferior to spirits of wine, inasmuch as they are liable to freeze” (Gannal 1840, 180). Gannal reported that Chaussier recommended the use of deuto-chloride of mercury (mercuric bichloride) in distilled water (Gannal and Harlan 1840, 166).
As late as 1884 it was reported that Albert Günther (1830–1914) at the British Museum was using 56 percent ethanol to preserve fishes. Because of the cost of ethanol, many other preservatives were also in use, including Goadby’s solution (composed of salt, alum or arsenic, mercuric chloride, and water) (Browne 1884). A chapter on “wet preparations” in a book on anatomical preparation techniques published in the early nineteenth century included as options alcohol; alcoholic solutions of a metallic, alkaline, or earthy salt; aqueous salt solutions; oils (particularly oil of turpentine); acids; acids and alcohol; alcohol and oils; and ammonia (Parsons 1831). Small amounts of elemental mercury were found in two alcoholic specimens of lizards collected and preserved prior to 1901 (Simmons et al. 2007). The mercury, presumably added to the preservative as mercuric chloride, had caused the specimens to noticeably darken. Mercuric chloride may be reduced to elemental mercury by the action of resistant heterotrophic bacteria, interactions with proteins, by reduction and oxidation reactions, or by interaction with an organic solvent such as ethanol.
As noted previously, vinegar has been used as a preservative, particularly for food, since at least the time of the Romans (Shephard 2000), and was a commonly used means of preservation in sixteenth-century England; the word pickle means to preserve in vinegar (Shephard 2000). Industrial methylated spirits (IMS), which is currently composed of ethyl alcohol denatured with methyl alcohol, went into duty-free production in Great Britain in 1855 (Derry and Williams 1960). According to Borodin (1930), during the mid-twentieth century there were two forms of denatured alcohol available under British regulations. Mineralized methylated spirits (100 gallons was composed of 90 percent ethyl alcohol, 9.5 parts wood-naphtha, 0.5 parts crude pyridine, 3/8 gallons mineral naphtha, and 1/4 ounce methyl violet dye) was sold for fuel and cleansing purposes. Industrial methylated spirits (95 percent ethanol and 5 percent wood tar) was sold for arts and industry purposes.
Summary
Preservation of organic materials in fluids has a long and often obscure history. Table 1 provides a compilation of published instructions for preserving organic materials in fluids; table 2 lists some of the most significant advances in the preservation of natural history specimens in fluid, beginning with Croone’s appearance before the Royal Society with his two preserved dog embryos in 1662. Two things that should be kept in mind while reviewing this history are the preponderance of chemicals used for preservation and the lack of rigorous testing of any of them. Because so many different chemical substances have been used outright or added to alcohol over the centuries, it is wise to use caution when working with older fluid-preserved specimens. Many of the chemicals reported in the literature are dangerous or downright toxic. The preservation of invertebrate specimens and anatomical preparations seem to have inspired a particularly diverse array of mixtures, brews, and solutions, as have (to a lesser extent) botanists trying to maintain the color of plants, but the bottom line is that any fluid-preserved specimen of unknown preservation history should be treated as potentially hazardous.
What is lacking in the literature (and in the practice of fluid preservation) are well-designed controlled studies that demonstrate which fluid preservatives really do work best for which organisms. Even such common practices as adding a little glycerin to alcohol preservatives (based on the assumption that should the preservative evaporate, the glycerin will form a coating on the specimens that will protect them longer from dehydration) have never been tested—we have, instead, proceeded for centuries to rely on oral tradition and anecdotal evidence to prepare the specimens that are then used in rigorous scientific work, with little attention to how preservation may have altered the specimens. Although the majority of the mixtures and additives that have been proposed since 1662 probably do not really improve the preservative qualities of ethyl alcohol, a few do merit further research, particularly the use of light oils (especially the proposal detailed in Chamberlin [1925]).