\ * . 



* * 



THE NATURE OF REPRODUCTION. 575 



depression or involution of its wall. From this point a slender neck, 



ending' in a rounded head, may be extruded by pressure ; after which 



the animal is seen to consist of a head and neck, terminated posteriorly 



by a dilated, sac-like tail, whence its 



generic name of cysticercus. Its specific FIG. 153. 



name is derived from its inhabiting the 



connective tissue, formerly known as 



The "cellular tissue." The head of the 



parasite, when magnified, shows upon 



its surface four sucking disks, and near 



its extremity a double crown of curved 



Calcareous processes Or hooks. There CYSTICERCUS CELLULOSE, from the flesh 

 -,. ,. i vi A. -i of the pig. Natural size. 1. Vesicular 



are no distinguishable internal organs, append a g e, with the head and neck ex- 



and the Caudal Vesicle Contains Only an truded. 2, 3. The same, with head and 

 -IV n -j mi. J.T- neck inverted; viewed in different po- 



albummous fluid. Thus there is no sitions ^^^ 



other apparent source for these organ- 



ism< than the tissues which they inhabit, nor have they any visible 



mode of continuing their species by generation. 



But it has been shown by Tan Beneden, Leuckart, Haubner, and 

 Kiichenmeister,* that Cysticercus cellulose is the embryonic progeny 

 of Tasnia solium, or the solitary tapeworm, found in the small intestine 

 of man. The specific identity of the two was first suspected from the 

 similarity of the head, which presents the same sucking disks and 

 crown of hooks in Tsenia as in Cysticercus. But in Taenia the neck, 

 instead of terminating in a vesicular appendage, is elongated and 

 wrinkled. The wrinkles, after a certain distance, become deepened into 

 superficial furrows, marking off the body into oblong articulations, each 

 articulation showing a double system of communicating vascular canals, 

 and distinctly-marked generative organs of both sexes. As they recede 

 by successive growth farther from the head, the generative organs be- 

 come more complete, and are at last filled with mature fecundated eggs, 

 in which the embryos are already partially developed. The tapeworm 

 then forms a chain or colony of articulations, sometimes from six to 

 eight metres in length, attached to the mucous membrane of the in- 

 testine by the minute head at its anterior extremity. 



By the experiments above mentioned it was found : 1st. That mature 

 articulations from the trenia solium of man, if administered to young 

 pigs with their food, produce a brood of cysticercus cellulose in the 

 flesh of these animals ; and, 2d. That cysticercus celluloses from measly 

 pork, if swallowed by man, becomes developed in the intestine, within 

 a few days, into ribbon-like worms, recognizable as young specimens 

 of taenia solium. 



The manner in which the pig becomes infested with cysticercus is 

 as follows : In the fully-formed tapeworm, in the human intestine, the 

 mature articulations separate from the rest of the colony, and either 



* Animal and Vegetable Parasites. Sydenham edition, London, 1857, pp. 115, 120. 



