By the time Lectures appeared in 1897, Pavlov was Russia’s most institutionally powerful physiologist by virtue of his positions at the increasingly prestigious IEM, the Military-Medical Academy, and the Society of Russian Physicians. Yet he enjoyed considerably more renown within the medical community than among members of his own discipline.
At the turn of the century he further strengthened his relations with clinicians by research on what he termed “the experimental pathology and therapeutics of digestion,” assigning coworkers to diagnose, cause, and treat various digestive ailments in dogs. In an address to the Society of Russian Physicians in 1899, he claimed that, although the practical results remained “trivial,” they signaled a new era of “experimental laboratory therapeutics” during which the lab would provide to the clinic, “efficiently and with complete competence, a purposive mode of action against specific illnesses.”1
The most impressive example concerned the survival of a dog with a double vagotomy. Physiologists had long been aware that this operation condemned an animal to death, and physiologist Moritz Schiff had recently hypothesized that a vagotomized animal perished from the disruption of its digestive system. In a dramatic presentation to the Society of Russian Physicians in 1896, Pavlov stirred his audience—and became a bête noire among Russian antivivisectionists—by displaying a vagotomized dog that he had kept alive for many months. He explained that, by first identifying the chain of events that led from a vagotomy to fatal digestive disturbances, he had been able to intervene effectively and preserve the animal’s health. “Here is a clear example of an entirely laboratory-based, rational therapy of a serious, fatal disturbance of the organism.”2
The various products of his physiology factory made solid if undramatic headway among Russian scientists. Pure digestive juices facilitated work in the burgeoning area of physiological chemistry by physiologist Alexander Danilevskii and two chemists at the IEM, Marceli Nencki and Ekaterina Shumova-Simanovskaia. Beginning in 1902, Efim London, head of the IEM’s Division of General Pathology, used a dog with a Pavlov sac in his pioneering studies of protein absorption. The great majority of coworkers returned to medicine after their tenure, spreading word about Pavlov’s achievements among physicians but doing little to enhance his stature in physiology. As of 1904, the lab had launched only a handful of alumni on a career in physiology. Pavlov’s favorite, Val’ter, had died in a train accident in 1902, prompting his lament that “there are no physiologists now, and they are needed.” Here he ignored two alumni who had become practicing physiologists, but brought him no solace: Aleksandr Samoilov had abandoned digestive studies for electrophysiology, and Lev Popel’ski had become a troublesome insider critic of Pavlov’s scientific conclusions. A cohort of future physiologists—Babkin, Boldyrev, Orbeli, and Savich—had not yet completed their doctoral theses.3
Pavlov was keenly disappointed by the response of Russian physiologists to Lectures. Serafima no doubt echoed his assessment in her recollection that the book “had no success at home in Russia.” The few reviews that did appear were positive, praising the author for his synthetic view of the digestive system, his contributions to methodology and technique, and the usefulness of his findings for medical practice. One reviewer even predicted that Lectures would “fundamentally change the reader’s view of the activity of digestive organs” and would become a “handbook for every physician.”4
Yet leading Russian physiologists wrote little or nothing about Pavlov’s work. Tarkhanov’s assessment in an authoritative review of Russian contributions to physiology at century’s end offered faint praise indeed: “I. P. Pavlov’s great significance consists in his introduction and perfection of a method to obtain various digestive juices in pure form.” Pavlov’s old acquaintance from Tsion’s circle, S. I. Chir’ev, now professor of physiology at Kiev University, wrote thirty pages on digestive physiology in his textbook Human Physiology (1902) without once mentioning his St. Petersburg colleague.5
Nor was he familiar to the Russian public. Unlike such popular figures as Ivan Sechenov and Dmitrii Mendeleev, he was neither a preeminent scientist nor a frequent writer and lecturer to lay audiences. When in 1901 a columnist for the popular weekly Niva reviewed the scientific legacy of the past century, he mentioned three Russian physiologists: Sechenov, Tsion, and Vvedenskii.6
Pavlov did, however, enjoy considerable professional success in these years. He was promoted in 1897 to full professor at the Military-Medical Academy, and his lab there, though no match for that at the IEM, was thoroughly renovated. In 1901, he shared the Academy of Science’s prestigious von Baer prize for scientific research. A committee chaired by Ovsiannikov concluded that “the experiments of professor Pavlov, thanks to the new methods he has introduced, have yielded such brilliant results by their precision that his name is inextricably linked with all the most significant data in the sphere of digestion.” Significantly, the Academy’s committee also noted that Pavlov’s Lectures had been translated into German, a sign of the “European reputation” much prized by Russia’s scientific community.7 Indeed, it would be his great successes in the West that vaulted him to the forefront of Russian physiology.
In the years 1891 to 1897, Pavlov published only infrequently in Western journals and eschewed international conferences. His few publications in Western languages concerned specialized subjects and lacked entirely the synthetic quality of his published addresses to the Society of Russian Physicians. During these years, edited versions of key doctoral theses appeared in the French edition of the IEM’s Archive of the Biological Sciences. Though not widely circulated, these did make some of the lab’s key findings accessible to Western specialists. Those specialists, however, did not cite Pavlov more frequently than they did his coworkers, and rarely credited him for their results.
The German edition of Lectures, which appeared in 1898, changed this dramatically. As Pavlov wrote in its preface (even before the Russian edition had appeared): “These [lectures] present a connected and complete review of everything that has previously been scattered among a dozen separate articles. Several of these articles are written only in Russian, others were published in the form of dissertations and reports to meetings and so remained entirely unknown to the scientific world of other countries.”8
The German edition owed much to Pavlov’s IEM colleague Marceli Nencki, who used his European contacts to find a good publisher, and, especially, to Pavlov’s favorite coworker of the time, Anton Val’ter. Author of the pathbreaking thesis on pancreatic secretion in 1897, Val’ter lavished attention on his German translation of Pavlov’s master work. Perhaps as a result of his affection for and familiarity with the chief, he succeeded in giving this translation the same authoritative, informal, and lively tone as the Russian original. His volume was followed in 1901 by a French edition and in 1902 by an English edition translated from Val’ter’s German.
Lectures was reviewed quickly, widely, and enthusiastically by physicians, physiologists, and other scientists in Western Europe and the United States. Reviewers did not fasten upon any single discovery, but rather commented consistently on the work’s great range, synthetic quality, and relevance to medical practice, and frequently identified it with the great possibilities of the new experimental biology and its modern laboratory system. The eminent physical chemist Wilhelm Ostwald praised Pavlov’s “lively language” and “brilliantly conducted experiments with animals,” but emphasized that his book exemplified a “scientific-practical method” that was transforming the very nature of science—the “collaborative work of master and comrades, where the latter are themselves on the path to becoming masters themselves.” The leading German specialist on digestion, Ismar Boas, pronounced Pavlov the successor to “the great era of Bernard, Ludwig, Heidenhain, and their schools,” and Hermann Munk, professor of physiology at Berlin University, concluded that Pavlov’s “enormous work” was comparable only to that of “Beaumont and Blondlot, and, recently, Heidenhain.”9
Reviewers were uniformly sympathetic to Pavlov’s argument for the specific excitability and purposiveness of the glands, and several noted his discovery of “definite periodic laws” for gastric and pancreatic secretion. Perhaps because mechanistic imagery in science and culture was so omnipresent and commonsensical as to be invisible, none mentioned his factory metaphor.
They consistently pronounced Pavlov’s monograph “indispensable” to both physiologists and clinicians. Boas predicted that “everybody working in the sphere of digestive illnesses will acquire from this book plentiful new ideas and impulses.” The reviewer for the Lancet urged Lectures on “all who practise medicine and who desire to have intelligent reasons for recommending to their patients systems of diet adapted to their particular derangements of digestion.” Pavlov’s advocacy of a close relationship between lab and clinic—and its embodiment in Lectures—featured in most reviews, as did the therapeutic significance of his findings, particularly his demonstration of the importance of appetite, the influences of various foodstuffs on the glands, the excitatory effect of hydrochloric acid upon the pancreas, and the secretory role of the vagus and sympathetic nervous system.10
The American biochemist Lafayette Mendel captured all these elements of Pavlov’s appeal in his short review in Science. “Among the comparatively recent contributions to physiological literature,” he wrote, “no book has exerted a more stimulating influence” than Lectures. Emphasizing the great range of Pavlov’s contributions, he praised the “brilliant Russian investigator” for a highly original work that had engaged both physiologists and practitioners while encouraging more active cooperation between them. Pavlov’s research was also interesting from “the general biological point of view” for its demonstration of the purposiveness of glandular operations. Mendel also mentioned a number of Pavlov’s specific findings and his development of new experimental methods. The Russian’s method for acquiring pure digestive juices, he noted, had acquired an importance independent of his scientific conclusions—that of facilitating research on their chemical composition. For Mendel, as for Ostwald, Pavlov’s work and lab embodied larger developments in science, demonstrating the striking progress of the new laboratory physiology.11
Pavlov’s various conclusions rapidly made their way into the specialized physiological literature and into textbooks. One important and revealing example is Johns Hopkins University physiologist William Howell’s American Text-Book of Physiology (1896, revised 1900). Howell read the German edition of Lectures, which structured his own discussion of pancreatic and gastric secretion. His textbook also illustrates dramatically that Lectures established the chief’s intellectual credit for the work performed by his coworkers. Compare one section from the first edition of Howell’s text, composed before the publication of Lectures, with the same section in the second edition of 1900. The author is discussing the nervous mechanisms of gastric secretion:
First edition, 1896
Some notable experiments recently made by Pawlow and Khigine [Khizhin]...have, however thrown some light upon this difficult problem...Khigine has made similar experiments, but altered the operation so that the isolated fundic sac retained its normal nerve-supply, which in Heidenhain’s operations was apparently injured. The results which he obtained are much more complete than any hitherto reported. He was able in the first place to determine the effect of various diets...
Second edition, 1900
The notable experiments recently made by Pawlow and his pupils...have, however, thrown some light upon this difficult problem.... This operation has since been modified by Pawlow in such a way that the isolated fundic sac retains its normal nerve supply.... Pawlow has been led by his interesting experiments to give a different explanation of the normal mechanism of secretion.... On a given diet the secretion will assume certain characteristics, and Pawlow is convinced....12
The content of these passages is identical, but in the post-Lectures version Pavlov emerges as lab chief and head of a school—and gains the intellectual credit for the isolated-sac operation and the discoveries that flowed from it.
Pavlov’s contributions also permeated Robert Tigerstedt’s Lehrbuch der Physiologie des Menschen (1898), which became the standard German medical textbook. When Pavlov sent Tigerstedt a copy of Lectures in 1898, the Finnish physiologist replied that he had relied upon it heavily to portray digestion in his Lehrbuch. “The summary of results on this subject in your lectures is extremely important. I am profoundly convinced that it will be received with great gratitude by other specialists.” Pavlov edited the Russian translation of Tigerstedt’s textbook in 1900, adding a laudatory preface and, no doubt with Tigerstedt’s approval, making some additions to the Finn’s discussion of digestion. Tigerstedt was quite pleased, and the increasingly warm relationship between the two physiologists would soon prove a great boon to his Russian colleague.13
The positive response to Lectures also spurred other developments that enhanced Pavlov’s international reputation. Because his findings and dog technologies were relevant to clinical practice and clinically oriented investigations, several Western physician-investigators—including Franz Riegel and Walther Clemm in Giessen and Heinrich Schüle in Freiburg—took these as the basis for their own research. Some reached conclusions fully compatible with Pavlov’s; others disagreed—but in each case Pavlov’s contributions found their way into medical discourse.14
Lectures also served to advertise Pavlov’s novel experimental methods and his laboratory design, generating a demand for these products and transforming his physiology division into the hub of an expanding network of contacts. Many Western scientists and physicians requested literature and counsel about specific methodologies, lab design, the acquisition of digestive juices, and the surgical creation of Pavlov’s unique experimental animals. Creation of these special dogs, however, required surgical skill, suitable facilities, and the craft knowledge acquired only through experience, and many Western scientists journeyed to St. Petersburg in order to learn from the master.
This demand for lab technologies did not depend on a scientist’s agreement with, or even interest in, Pavlov’s specific findings. A sizable contingent among the lab’s correspondents and visitors were physiological chemists interested in the biochemistry of ferments and proteins and the process of protein absorption—research that was rapidly moving scientific discussions of digestion away from Pavlov’s beloved organ physiology. Indifferent to Pavlov’s purposive secretory curves, the nature of appetite, and the innervation of the gastric glands, they wanted to learn how to produce lab dogs that would provide a reliable supply of pure digestive juices.15
The experiences of several visitors in 1902 illustrate the value of Pavlov’s lab products to a range of clientele, and the way this built his network. The Dutch physician F. A. Steeksma informed Pavlov after his visit that “I have begun to conduct the very same experiments as I conducted in your laboratory and intend to acquaint my colleagues in Holland with them at the April 1903 Holland Congress of Physicians, where I will demonstrate several operated dogs.” He also passed on a colleague’s request for medical advice: this physician was treating a patient who, after an operation to remove a stone, had a fistula of the bile duct. The patient was now suffering from a softening of bones, “exactly like that in [Pavlov’s lab] dogs.” Would Pavlov please tell him how to treat this condition?16
Pathologist Walther Gross spent four months in Pavlov’s lab in early 1902, during which time he worked on gastric digestion. After returning to Heidelberg, he wrote an article based on this research and sent it to Pavlov for his inspection. Shortly thereafter, Gross became an assistant to Friedrich von Müller at the medical clinic of Munich University. With Müller’s encouragement, Gross soon requested a return trip to St. Petersburg in order to “master your surgical methods on dogs and conduct work in your laboratory under your guidance.”17
The most eminent visitor of 1902 was Professor Otto Cohnheim of Heidelberg University. Before his trip to St. Petersburg, Cohnheim had published a book on protein chemistry, and in 1901 identified an enzyme, erepsin, that prepared proteins for absorption into the blood. In 1902 he was investigating the origin of erepsin and its site of action, and thought Pavlov’s dog technologies would facilitate this research. After returning from St. Petersburg, he wrote an appreciative letter: “You greeted me with such kindness and so readily showed me your new and most interesting investigations that I will all my life recall with the greatest satisfaction the wonderful weeks...in your laboratory. I will soon begin to conduct here the operations I studied [in St. Petersburg].” Five years later, Cohnheim informed Pavlov that “our Institute is completely adapted for surgical operations and I will diligently conduct the operations that I studied under you.” In 1910 he sent Pavlov a number of his recent articles, “from the content of which you will see that I have become your diligent student.”18
Another leading physiological chemist, Emil Abderhalden, wrote to Pavlov in October 1904 to request assistance in the creation and maintenance of a dog with a pancreatic fistula. Abderhalden was collaborating with Hermann Fischer, who had won the Nobel Prize in Chemistry two years earlier. “For the splitting of synthetic polypeptides we need the most active pancreatic ferment possible,” he explained. “I would be very grateful if you would be so kind as to advise me, having such valuable investigative experience, how one can preserve the life of the operated-upon animal as long as possible, what nutrients it needs, and how best to care for it. It would also be very important for me to know how I can acquire the most active juice.” Pavlov responded by sending both some digestive juices and his assistant Boris Babkin to Berlin, where Babkin labored unsuccessfully to create the necessary dog technology in Abderhalden’s lab. When Babkin concluded that the operative facilities there were inadequate, Pavlov sent a deeply grateful Abderhalden the necessary digestive juices. Many years later, Abderhalden recalled that, this technical assistance aside, the Russian physiologist had influenced him profoundly. “As a young student I was fascinated by your remarkable experiments on the secretion of digestive juices, and from that time you have been my teacher. I cannot find the words to express my debt to you.”19
Pavlov’s growing international reputation was reflected in these years by his election to a series of honorary memberships, beginning with Mexico’s Antonio Alzate Scientific Society in 1898. By 1904 these had been conferred by scientific and medical societies in Uppsala, Stockholm, Helsingfors, Copenhagen, Berlin, Vienna, Paris, and New York. When he traveled to Paris in 1900 for the International Congress of Physicians—his first foreign trip in fifteen years—he did so as one of the Congress’s honorary presidents.
The publication of Lectures and the enthusiasm of the lab’s medical alumni also spurred sales of Pavlov’s therapeutic contribution to scientific medicine: the “natural gastric juice of the dog” as a remedy for dyspepsia. “Appetite is juice,” Pavlov reminded readers of Lectures. “To restore a person’s appetite means to give him a large portion of good juice at the beginning of a meal.” Especially in the “nervous century,” hurried people often ate their meals with inadequate attention, and so failed to produce the plentiful and ferment-rich “psychic secretion” that lab research had demonstrated was critical to the proper digestion of food.20 Pavlov’s nostrum had caught on less quickly in Russia than in Germany and, especially, France. There one physician, Frémont, marketed his own variety under the name of “gastérine,” and a spate of articles by physicians lauded the remedy. This forced Pavlov to insist upon his priority in an article of 1896 and, in Lectures, to note the superiority of his own variant and make a patriotic plea to his countrymen: “Will it prove the case that this product long known to us will be more successful under a foreign flag?”21
Former coworkers, some of whom had apparently benefited from this home remedy in Pavlov’s lab, became effective apostles of gastric juice therapy in Russia. In his article “The Old and the New in the Sphere of the Secretory Function of the Stomach,” Abram Virshubskii outlined the “new doctrine” on digestion that had emerged from Pavlov’s lab and proselytized for the gastric juice therapy it had produced. “I personally have been drinking it for three months,” he wrote, “taking 20–25 cc. once or twice a day after eating, and am indebted to it for the disappearance of continual diarrhea and meteorism. Others drank 40 cc. at a time with good results in the sense of the easing of the subjective symptoms of dyspepsia.” The efficacy of gastric juice therapy testified to the great clinical promise of scientific physiology. “The radical reform of gastric physiology is inevitably reflected in the pathology and therapeutics of this organ.”22
Other Russian physicians were also drawn to the new scientific remedy. Some, such as A. A. Finkel’shtein, visited the lab in order to learn how to establish their own operation. Reporting on the encouraging results obtained with patients suffering from a wide variety of gastric ailments, he agreed that it constituted a “new, powerful, therapeutic agent.”23 Pavlov shared his production secrets enthusiastically. Rather than patenting his remedy—which would have violated his fervent belief that science should not be practiced for profit—he and his coworkers actively encouraged others to produce it themselves, providing the necessary information in theses, articles, and Lectures itself. For him, the greatest value of this enterprise was its dramatic illustration of the benefits of scientific physiology—and his lab, in particular—to the clinic. For precisely this reason, perhaps, he insisted on marketing his product as “the natural gastric juice of the dog” despite the revulsion it provoked among some potential customers. That term, unlike Frémont’s market-savvy “gastérine,” emphasized its origin in experimental physiology, in the understanding and manipulation of the laws governing living organisms.
Yet the financial benefits were also quite substantial and made a critical difference in the life of the lab. The IEM was strapped for funds, and the budget for its divisions remained essentially flat from 1891 to 1914—but gastric juice sales increased Pavlov’s operating budget by about 70 percent by 1904 and more than 500 percent by 1914.24
Between 1898 and 1901, growing domestic sales of gastric juice and, especially, Pavlov’s influence with Prince Ol’denburgskii led to the establishment of a full-fledged “small gastric juice factory” at the IEM. An assistant was hired and paid thirty rubles a month to oversee the facility. Here, on the ground floor of the lab, five large young dogs, weighing sixty to seventy pounds and selected for their voracious appetites, stood on a long table harnessed to the wooden crossbeam directly above their heads. Each was equipped with an esophagotomy and fistula from which a tube led to the collection vessel. Each “factory dog” faced a short wooden stand tilted to display a large bowl of minced meat. Large, hungry dogs could produce up to 1,000 cubic centimeters of juice in one session.
As Pavlov delighted in pointing out, this gastric juice factory was powered by appetite. In his lectures at the Military-Medical Academy, he proudly demonstrated the operation of this physiological perpetual-motion machine:
Yesterday somebody asked me: why does the dog not refuse to eat? I must tell you that I have had hundreds of such dogs and not one behaved as your comrade suggested.... they eat in the most marvelous fashion until their jaws become tired. Well, of course, this is a sham meal, a physiological perpetuum mobile...does it guess that it is being deceived? That is for the dog to know. What, after all, stimulates us to eat? Necessity. But the dog has this very same necessity, even more so, because it eats and eats and is not satisfied. You have heard from history that in dissolute times Roman gentlemen would feast and then take purgatives and again begin to eat. And this is people—but the dog does as God commands. With its operation it needs no purgatives. Eat as much as you wish!25
This was scientific medicine at its best—understanding and control of the animal organism in the therapeutic interests of humankind.
* * *
Even as Pavlov enjoyed his growing reputation in the first years of the new century, cracks began to appear in the intellectual edifice he had constructed. Three related developments combined to cast doubt on some of his central claims, to devalue and even discredit one of his key dog technologies, and to shift study of the digestive glands away from organ physiology. First, growing attention to the interaction and biochemistry of ferments cast doubt on the conclusions Pavlov had drawn from the regularities he perceived at the organ level and signaled an important shift in scientists’ attention toward issues that were resolvable only at a sub-organ level. Second, Pavlov’s former coworker Lev Popel’skii published several articles subjecting Pavlov’s concept of purposiveness, and the quantitative data used to support it, to a damaging insider criticism. Finally, Bayliss and Starling’s discovery of secretin undermined Pavlov’s nervist portrayal of pancreatic secretion and generated a growing interest in the humoral mechanisms of the digestive apparatus. All three developments resulted in part from discoveries in Pavlov’s lab.
Before the publication of Lectures, Pavlov had devoted little attention to the lowly intestines. In 1897, however, he assigned N. P. Shepoval’nikov to investigate intestinal secretions, and two years later the coworker reported a stunning (and potentially disturbing) fact: the addition of intestinal juice to pancreatic juice raised the strength of all three pancreatic ferments and transformed the albuminous ferment from a zymogenic (inactive) form into an active form, trypsin. Describing Shepoval’nikov’s finding in an address to the Society of Russian Physicians in 1899, Pavlov termed the newly discovered agent “enterokinase” (from the Greek for “intestinal” and “move” or “excite”). For Pavlov, this “ferment of ferments” represented a further mechanism for the precise and purposive work of the digestive glands.26
This discovery, however, also had another, disturbing implication—it suggested that dogs with Pavlov’s pancreatic fistula were “abnormal” and that the data they generated were flawed. In these dogs, pancreatic juice flowed out over a piece of the duodenum and so might well be affected by enterokinase. This raised the possibility that the fermenting power of the pancreatic juice analyzed by Vasil’ev and Val’ter had been selectively—and even idiosyncratically—raised by the “ferment of ferments.” Because enterokinase acted most decisively on one of the three pancreatic ferments—and because the lab had not been aware that it was dealing with secretions that were in some combination of zymogenic and active states—the data used to conclude that the pancreas responded precisely and purposively to various foods may well have been skewed. At a meeting of the Society of Russian Physicians, Pavlov conceded that, with the benefit of hindsight, there had been indications of this possibility. Yet he minimized the importance of this complicating factor and continued to rely on his standard pancreatic fistula.27
His lab, however, did not monopolize discussions of this question. Twenty-five years earlier, Heidenhain had obtained from the pancreas a substance that did not itself possess proteolytic power but from which he could acquire an active ferment. He had named this substance “zymogen,” a term that by the late 1890s was commonly used for this entire class of substances (sometimes referred to as “precursors or “proferments”). By this time, scientists were studying the chemical and physiological processes that converted digestive zymogens to active enzymes—transforming, for example, the pepsinogen secreted by the gastric glands into pepsin, and the trypsinogen secreted by the pancreas into trypsin.28
In 1902, two physiologists at the Pasteur Institute, Camille Delezenne and Albert Frouin, built upon the discovery of enterokinase to deliver what they characterized as a “severe blow” to Pavlov’s views. Using a catheter to obtain pancreatic juice that had not passed over the duodenum, they concluded that the juice “does not possess its own digestive action vis-à-vis albumin.” Under normal physiological conditions, then, pancreatic juice possessed no proteolytic power until it combined with the enterokinase secreted by the duodenum. Yet Pavlov and his coworkers had claimed to measure the varying proteolytic power of pancreatic secretion in response to various foods—and had built their characteristic curves upon just such data. Pavlov’s evidence for the precise, purposive adaptation of pancreatic secretion, Delezenne and Frouin concluded, was but the artifact of experimental error. By this time, the Frenchmen could cite two other investigators, one German and one Russian, who had independently reached the same conclusion.29 Pavlov assigned Babkin to check the French physiologists’ results. Babkin raised questions about the normalcy of their dog technology and questioned some of their specific conclusions, but he confirmed their critique of the pancreatic fistula and the results based upon it.30
These developments proved only the beginning of increasingly complex discussions about the physiology and chemistry of digestive secretions, discussions in which some members of Pavlov’s lab group, including Babkin and Savich, would participate actively. The question of the adaptiveness of pancreatic secretions was not settled and would prove contentious for decades to come. Yet this challenge did undermine one of Pavlov’s key claims and signaled a far-reaching change in the very nature of scientific discourse on digestion.
That discourse was spiraling away from organ physiology toward studies of intermediary metabolism. Fueled by the increasing intellectual and institutional power of physiological chemistry, the center of gravity in digestive physiology was, then, moving away from Pavlov’s aesthetic preferences and intellectual strengths and toward an area in which he neither enjoyed technical supremacy nor spoke with special authority.31
Sometime in 1902–1903, his former coworker Lev Popel’skii visited the lab for a talk with the chief that ended with a vintage explosion of Pavlov’s temper. Babkin witnessed the aftermath:
After a stormy interview in the laboratory at the Institute of Experimental Medicine, Pavlov broke off relations with Popielski completely and refused to shake hands with him on parting.... The scene took place in Pavlov’s study on the second floor. We heard loud shouts and then down the small winding staircase leading to our room came Popielski, almost falling downstairs in his hurry, and red as a lobster. He quickly put on his coat and went out, without saying goodbye to anyone. After this there was dead silence and it was a long time before Pavlov appeared.32
Popel’skii belonged to the small group of coworkers who, at the turn of the century, seemed to comprise the nucleus of a genuine “Pavlov school” of future physiologists. He differed from the other members of this cohort, however, in two important respects. First, as a graduate of the mathematics division of St. Petersburg University, he could engage in quantitative reasoning with some comfort and authority. Second, he had decided on a career in physiology and begun to acquire expertise in that discipline before working with Pavlov. As Tarkhanov’s assistant in the Physiology Department of the Military-Medical Academy from the early 1890s through 1895, Popel’skii had begun research on the influence of cocaine, ether, and alcohol on nervous excitability. When Pavlov replaced Tarkhanov in 1895, Popel’skii remained as assistant and conducted doctoral research under Pavlov’s guidance. Popel’skii, then, viewed himself not as a mere pair of “skilled hands” but as a physiologist in his own right.
His doctoral thesis, On the Secretory-Inhibitory Nerves of the Pancreas (1896), proved to be the high-water mark for nervist explanations of pancreatic secretion. Here Popel’skii (with Pavlov’s support) argued that two sets of nerves—one excitatory, the other inhibitory—joined the vagus to the pancreas, providing a nervous regulator to the secretion elicited by hydrochloric acid. His thesis also reflected an intellectual independence unusual for coworkers: Popel’skii cited literature from outside the lab, employed a considerable amount of first-person-singular language, and did not use Pavlov’s favorite words for describing physiological processes. In particular, the word “purposive” did not appear even once. He appended a proposition to his thesis that expressed his problem with this concept so dear to the chief: “The question of the specific exciters of the digestive glands requires further, serious exploration.”33
From 1901 to 1903, while serving as a military physician in Moscow, Popel’skii published a series of articles criticizing Pavlov’s notion of “purposiveness” and the quantitative data on which it was based. Using the lab at the Moscow Military Hospital, he also employed Pavlovian techniques and dog technologies, particularly the improved pancreatic fistula, to advance an alternative view of the differing glandular responses to various foods.34
Unlike outside reviewers of information and conclusions generated by Pavlov’s lab, Popel’skii analyzed in detail the relationship between the experimental data generated by coworkers and the conclusions based upon them. “The facts,” he argued, “cannot be considered convincing,” and he repeatedly noted “a certain subjectivism in interpretation.” When confronted with complex phenomena, Popel’skii observed, scientists frequently become “the victim of enthusiasm for some preconceived idea”; Pavlov’s attachment to “purposiveness” had so misled him that his theory “cannot be considered strictly scientific.”35
Popel’skii also observed that Pavlov simultaneously insisted on two incompatible propositions: first, that the amount and ferment content of pancreatic secretion elicited by particular food followed the stereotypical courses identified in Val’ter’s thesis; and, second, that the secretory pattern of the pancreatic gland adapted over time to an animal’s diet. If the latter claim was true, how could any one animal produce the “stereotypical” secretory pattern identified in the first proposition? Pavlov’s investigative assumptions were also, in Popel’skii’s view, biochemically unsupportable—making his “success” in discovering particular patterns doubly suspect.36
The secret of this success, he suggested, resided in the tendentious interpretation of data. Analyzing in detail the key doctoral theses on the purposiveness of pancreatic secretion, Popel’skii pointed to significant differences in the results of identical experiments and to a consistent pattern of ignoring differences within a category (say, experiments on the secretory response to feedings of meat) while emphasizing lesser differences between categories (for example, between the secretory responses to meat and bread). For him, the experimental data actually fit a pattern that was precisely opposite to that predicted by Pavlov’s doctrine: with only minor exceptions, the proteolytic power of all three ferments rose or fell together. There was no evidence, then, for the specificity—let alone the purposive specificity—of pancreatic responses to the three foods.37
Rejecting Pavlov’s belief in “a variety of specialized irritants” and nerve endings, Popel’skii argued that physical and chemical exciters all acted on the same nerve. The quantity and proteolytic power of pancreatic secretions depended simply on the amount and strength of the exciters. As for Pavlov’s insistence that the amount and ferment content fluctuated independently, Popel’ski suggested that juice that seemed weak in proteolytic power was actually strong in proferment, and so became fully active only seven to ten hours later.38
Popel’skii first advanced these arguments in Russian, in a preliminary communication in The Physician in 1901 and a detailed exposition in Russian Physician in 1902–1903. That, no doubt, would have sufficed to infuriate the chief. One can imagine Pavlov’s reaction to the republication of Popel’skii’s preliminary report in Deutsche Medicinische Wochenschrift (November 1902) and to the appearance of a second article, which detailed Popel’skii’s experiments undermining Val’ter’s thesis, in the leading European physiological journal, Centralblatt für Physiologie (May 1903).
This, then, was the background to Pavlov’s rage at his former coworker and to the scene that Babkin witnessed. Popel’skii’s had breached the moral economy of “We, The Laboratory,” contradicting the chief publicly—and at an exceptionally sensitive time. As Pavlov was well aware, he was being considered for a Nobel Prize, and the questions raised about his analysis of pancreatic secretion were figuring importantly in the committee’s deliberations.
An even more profound challenge was arising. By the turn of the century, scientists’ view of the body was changing, with increased attention to the role not just of cells and nerves, but of bodily fluids. When Pavlov had imbibed his basic physiological views in the 1870s, such “humoralism” had been regarded as a relic of prescientific, Hippocratic beliefs. But increasing attention to internal secretions and new immunological theories that emphasized the role of animal serums were now creating a new “humoralist tide.”39
That tide reached the digestive system in 1902 with William Bayliss and Ernest Starling’s discovery of secretin. The British physiologists had been following up Dolinskii’s 1893 discovery in Pavlov’s lab that the introduction of hydrochloric acid into the duodenum elicited a pancreatic secretion. Pavlov had largely ignored this indication of a possible humoral agent, but Bayliss and Starling concluded that hydrochloric acid acted upon a precursor stored in the mucous membrane of the duodenum to produce an active substance, which they named “secretin.” Traveling through the blood, secretin excited pancreatic secretion.
They quickly incorporated their discovery into a broad vision of the regulation of bodily processes that assigned much the same role to humors as Pavlov assigned to nerves. Also like Pavlov, they were able to mobilize the research of other investigators, including Francis Bainbridge, who in 1904 provided a humoralist explanation of the adaptation of pancreatic secretion to various foods, and John Edkins, who in 1905 announced his discovery of gastrin, a humoral agent of gastric secretion.40
Bayliss and Starling soon dismissed Pavlov’s belief in nervous mechanisms of pancreatic secretion to experimental error. As for gastric secretion, they accepted his demonstration of the nervous character of the first, psychic phase, but rejected any role for “any such obscure mechanisms” in the second phase, when food was processed in the digestive tract.41
The British researchers also finally rejected Pavlov’s central contention that the glands responded purposively and precisely to various foods to generate “characteristic secretory curves.” The Russian’s evidence for this, they observed, was “not absolutely convincing.” With respect to the pancreas, the discovery of enterokinase had invalidated Pavlov’s experimental procedures and, as Popel’skii had demonstrated, the data in Val’ter’s key thesis “do not entirely bear out his conclusions.” As for the gastric glands, any specific secretory response to particular foods could be explained without recourse to Pavlov’s specific nervous exciters: “As a rule the more indigestible the foodstuff the longer will it remain in the stomach; the greater, therefore, will be the secretion of acid gastric juice.”42
Bayliss and Starling’s “chemical correlation” of digestive functions differed fundamentally from Pavlov’s precise, nerve-governed digestive factory. For them, neither the pancreas nor the stomach responded “purposively and precisely” to the requirements for digesting a particular food. Rather, each gland was stimulated by a single chemical agent to release its stock of ferments. This process was coordinated by what they termed “chemical reflexes.” First, the peptogenous substances created in the stomach by the contact between psychic secretion and food led to the production of gastrin, which released the stomach’s stock of ferments. Next, the acid produced by gastric digestion led to the production of secretin, which excited both the release of pancreatic ferments (and proferments) and the secretion of bile. Bile salts, in turn, “doubled or tripled” the strength of the fat-splitting and starch-splitting ferments in pancreatic juice. Thus, by exciting both glands simultaneously, secretin coordinated the timing and volume of their secretory activity. Bayliss and Starling predicted the discovery of a similar mechanism—also “of a chemical nature”—that synchronized the activity of the pancreas and the duodenum. The efficient functioning of the digestive system resulted, then, not from nervous mechanisms that fine-tuned the secretions of each individual gland, but rather from chemical mechanisms that coordinated the gross activity of these glands as a whole.43
There followed decades of experiments and interpretive conflicts about the role of nerves, humors, and the psyche in digestive processes. Experiment was piled on experiment, interpretation on interpretation, and methodological quarrel on methodological quarrel. Pavlov himself, however, was little interested and poorly equipped to participate—this was not his kind of digestive physiology, and he would soon abandon the subject entirely.
* * *
The year 1904 marked the twenty-fifth anniversary of Pavlov’s graduation from medical school and so, according to Russian academic tradition, offered an occasion for official celebration of his achievements. He disliked official festivities and torpedoed those planned by the Academy of Sciences and the Military-Medical Academy by threatening to leave St. Petersburg on the days they were scheduled. He did consent, however, to a celebratory meeting at the Society of Russian Physicians, and his jubilee was also marked by congratulations from numerous scientific and medical societies, a photo album celebrating his achievements, and a special volume of the IEM’s journal devoted to reminiscences and scientific articles honoring his scientific achievements.
As the Parisian physiologist J. P. Langlois observed, Pavlov’s reputation had so completely “breached the frontiers” that physiologists transformed his jubilee into a manifestation mondiale—a worldwide demonstration of respect for his achievements.44 Langlois had in mind the celebratory volume of the IEM’s Archive of the Biological Sciences, which was dedicated to Pavlov from his admirers. This volume reflected the great range of his contributions to science and medicine, testified to his international reputation, and codified the existence of a “Pavlov school.”
The Russian contributors included Pavlov’s friend David Kamenskii, who described the chief’s early days in the Botkin lab, and a former coworker who reported his clinical successes in the treatment of dyspepsia with “the natural gastric juice of the dog.” Two Russian professors of physiology, Danilevskii and Tarkhanov, also contributed articles—although neither cited Pavlov’s work and Tarkhanov could manage only a two-page abstract. Four of Pavlov’s coworkers and colleagues contributed an annotated bibliography of 139 “works of I. P. Pavlov and his pupils.” The eleven contributions by Westerners included a warm biographical sketch by Tigerstedt and scientific articles by leading European authorities (many of whom had visited Pavlov’s lab) in physiology, pathology, physiological chemistry, and pharmacology. Among them was William Bayliss, who, despite his criticisms, viewed Pavlov as the founder of modern digestive physiology.45
Describing the reasons for this manifestation mondiale to readers of La Presse Médicale, Langlois portrayed Pavlov not merely as the discoverer of a dazzling array of scientific facts but as the very embodiment of modern physiology, a visionary, and even a wizard. Having visited the IEM lab in February 1904, Langlois explained that it was there, “among the numerous students that he directs and inspires, that one must see Pavlov.” Pavlov resembled Langlois’s “venerated master,” the celebrated physiologist Charles Edward Brown-Séquard, by his physical and intellectual vivacity and his love for his collaborators. Also like Brown-Séquard, Pavlov had, in earlier years, shared his own modest lodgings with his experimental animals. That, however, was a bygone era. Now, “the small room in a narrow alley has been singularly transformed: Pavlov’s laboratory, constructed according to its master’s instructions, can be considered a model of its genre.” His greatness could be fully appreciated only by seeing the lab in operation and by reviewing all the works produced there by the master and his pupils. These investigations were “guided in their every step by therapeutic concerns” and united by a single “directing idea, the same philosophical conception”—“to demonstrate the adaptation of all the organs to accomplish the best for the entire organism in its vital processes.”
Lovingly describing the surgical facilities of Pavlov’s physiology division—“a milieu that is identical to the best hospital’s operating room”—Langlois testified that the dogs, like Pavlov’s coworkers, were enraptured by their master: “All these dogs, with their double or triple fistulas, have a particularly gay air, and welcome the arrival of their master with expressions of joy. The dogs who are manufacturing gastric juice, pancreatic juice, and saliva, suspended by a double strap under their belly, interrupt their abundant ‘sham meal’ to cast their gaze at Pavlov and to request his habitual caress.”
Langlois’s Pavlov, then, is considerably more than the sum of his laboratory’s products. He is the beloved master of a modern laboratory and everything within it—not merely nerves and glands, but coworkers and dogs. He collects both the juices and the affection of his experimental animals, who, despite the rattling of their sophisticated technological apparatus, retain recognizably pet-like characteristics. As a visionary and the master of a modern laboratory system that produced so many diverse products, Pavlov thus embodied an appealing synthesis of some troublesome polarities: efficient production and scientific imagination, laboratory physiology and medical practice, precise science and the complexities of living creatures. “The Russian master,” concluded his French colleague, “occupies the very pinnacle in the domain of experimental medicine.”46