124 
ME. EAIKET ON THE STEHCTUEE AND DEYELOPI^IENT OF THE 
when charged with fertile ova or embrj^os, may separate in due time from its neighbours, 
a single segment has been looked on as constituting a distinct being, and is named a 
proglottis. 
The evidence of the conversion of cystic into cestoid entozoa is ample. A particular 
form of Cysticercus grows into a particular species of Tmiia, of which it is the scolex ; at 
least this definite specific relation is probable ; and it has now been shown, by numero us 
and varied experiments, that when Cysticerci are given to an animal with its food, they 
gradually pass into Toenioe, provided the Cysticercus made use of is the true scolex of a 
species of Tmnia capable of being harboured by the animal subjected to experiment. 
The Tcenice thus produced agree in number with the Cysticerci swallowed, at lea§t never 
exceed them ; they may be traced in progress of development, and when given success- 
ively at suitable intervals, the resulting Tcenice present corresponding differences of 
advancement. 
The Cysticercus cellulosoe is, believed to be the scolex of the Tcenia solium, which infests 
the human alimentary canal ; and in an experiment made on a condemned criminal, 
these cystic parasites put into the food a short time before execution were afterwards 
found in the intestine converted into incipient Tcenice, recognizable as the Tcenia solium. 
The Tcenia being thus developed from the Cysticercus, it should naturally follow that 
the Cysticercus is, in its turn, derived from the Tcenia ; and the fact is estabhshed by 
experiments which may be regarded as complementary of the former. Matui’e segments 
of tape-worm, full of embryos, have been given to different animals with them food, and 
the tissues of these animals have become infested Avith Cysticerci. In this way the Tcenia 
coenurus, given to sheep, has been followed by the production of Ccenurus cerehralis in 
the brain of these quadrupeds ; Cysticercus fasciolaris has been produced in mice ffom 
the Tcenia crassicollis of the Cat ; Cysticercus pisiformis has been generated in rabbits 
from embryos of the Tcenia serrata of the Dog ; and, not to mention other cases, pigs 
have become infested Avith the Cysticercus cellulosce, after receriing AAdth their food ripe 
segments of the Tcenia solium of the human subject. Moreover, Steix foimd in the 
alimentary canal of the larvse of Tenehrio molitor, the usual six-hooked embryos of an 
undetermined species of Tcenia, and on the outer or peritoneal smfface of the stomach of 
the same larvae, numerous encysted Cysticerci, on nearly all of which the six booklets 
shed by the embryo could be perceived adhering to the cyst and thus clearly shoAving 
the connexion of the two. In like manner Meissxer found cysts containing Cysticerci 
in the body of the Slug; and although he did not discoA'er Tflg^zm-embryos, he found what 
were unmistakeably their six booklets attached to the body of the Cysticercus. 
While, however, the proof of the derivation of the Cysticercus fi’om a Tft’?»’«-embryo 
thus seems complete, the process of conversion of the one into the other has not hitherto 
been followed completely in its different steps. The observations of Leuceaet on this 
head are perhaps most to our present purpose. He found, that on griing the OA a of 
Tcenia serrata to rabbits, a numerous brood of Cysticercus pisiformis appeai-ed in the 
liver, which situation he conceives they might have reached by the route of the vena 
