8 PARASITES OF MAN. 
Intermediate host.—Not required. 
Experiments.—Leuckart reared intra-ovular vermiform embryos 
by placing the eggs in moistened paper envelopes and exposing 
them to the action of the sun’s rays. Heller reared them in glass 
tubes filled with saliva and carried about under the arm-pits. 
Hellerand Zenker possessed themselves of specimens of the higher 
larves from the small intestines (post mortem) in a case where the 
patient had swallowed the eggs some days previous to his death. 
I caused a monkey to swallow a quantity of eggs in the hope of 
rearing the adult parasites, but the the result proved negative. 
Possibly at the post mortem examination I overlooked the 
existence of larvee, but I do not think any were present. Lest 
some persons should suppose this kind of experimentation to be 
unwarrantable, I may remark that it had for its object the 
alleviation of human suffering. Others have experimented upon 
themselves with the same benevolent purpose. Thus, Professor 
Leuckart and three of his pupils infested themselves by courage- 
ously swallowing a quantity of the ova. They certainly enjoyed 
the satisfaction of subsequently supplying ocular proof of the 
success of their worm-feedings. 
Remarks.—The common notion that these parasites breed within 
the human body is an error, and it is equally incorrect to say 
that they reside in the lowermost part of the intestinal canal. 
Their head-quarters are the cecum and upper part of the colon. 
It is true that Vix and Leuckart have noticed embryos within 
the large intestine; but Leuckart, Heller, and myself alike 
regard this intestinal hatching as an unusual occurrence. For 
the purposes of infection it is alone necessary that the eggs of 
the worm be conveyed to the mouth and swallowed. Their 
previous immersion in water for any length of time secures their 
destruction, by the bursting of the egg-shells consequent upon 
endosmosis. The eggs are conveyed to the mouth in various 
ways. Ordinarily, children become infested by biting their nails, 
beneath the margins of which the eggs lie concealed. Professors 
Heller, Zenker, and myself have, all mort or less, frequently 
had occasion to demonstrate this fact to our patients. Occa- 
sionally, the eggs are swallowed by accident during sleep. Still 
more rarely whole parasites may be conveyed to the mouth in a 
similar manner. In whatever manner they may have been 
conveyed to the bearer, when once the eggs have gained access 
to the stomach, their shells are dissolved by the action of the 
gastric juice, and the larvae are liberated. Inthe upper intestine 
the larve grow rapidly. Here they undergoone or more changes 
of skin ; acquiring sexualmaturity within a period of less than a 
month. 
Literature.—All standard works. See also my lectures on 
Helminthology, (‘‘Worms,”) and more particularly the very 
admirable article (Darmschmarotzer) by Heller, in Yon 
Ziemssen’s ‘Handbuch,’ or the recently issued American 
edition of the same work. 
38.—Leptodera stercoralis, Bavay. 
Syn.—Anguillula (Rhabitis) stercoralis, Bavay. 
Larve.—These are at first known as minute embryos, measuring 
only ;4, of an inch in length. Subsequently, in the condition of 
immature rehabitiform larve, they acquire alength of about , 
of aninch. All their changes of size and shape, accompanied 
by ecdysis, are undergone within the human intestine. Under , 
