Addendum to my last communication on the invasion of Taenia elliptica and Ascaris*
ADDENDUM
I recently conducted an experiment that entailed allowing the eggs of Ascaris lumbricoides with an outer gibbous coat pass through the intestinal tract of an adult human being in good health. The eggs were again enclosed in a little bag of parchment paper, which was eliminated 12 hours after swallowing. The bag was then washed in warm water and carefully opened, and the contents placed under a microscope. There were several hatched embryos that executed lively serpentine movements and occasionally coiled into a spiral. Despite gradual cooling, their movements could be observed for sometime. The empty mulberry eggs1 displayed hatching points in different places. A few eggs still contained embryos that were clearly alive; others displayed different stages of segmentation. The outer mulberrylike coat was preserved in all of them.
A second, analogous experiment, in which passage through the body took 20 hours, showed a larger number of hatched embryos. However, the attempt to achieve further development by keeping the bag at body temperature was unsuccessful, probably because advanced putrefaction killed the embryos. The shape of the head of all living worms was that of a truncated cone, fitting Leuckart's description of the outer cuticle (which, according to him, carries a thickened chitin plug) but not the perforating tooth of the 2nd cuticle. (These details were not distinctly perceptible.)
Having now shown that living embryos can hatch from eggs with mulberry coats inside man's digestive tract, proof is now needed that they continue to develop there. I shall attempt to furnish this proof shortly.
São Paulo, January 12, 1888