258 DISEASES OF THE DIGESTIVE APPARATUS. 



a cuticiila, and also by an internal layer containing tlie genital 

 apparatus and the vascular trunks. The genital apparatus is her- 

 maphrodite; it is represented by the uterus, ovary, vagina, and 

 vulva, on one side, and by the testicles, the deferent canals, and 

 the cirrus, on the other side. The genital orifice is almost always 

 located upon one of the edges. The eggs, which are very abundant 

 in the uterus, possess a very hard membranous shell (embryophore) 

 covering a globular embryo, which is clear, and provided with four 

 or six hooks ; they are extremely resistant, but dryness kills them. 

 When these eggs reach the stomach of a vertebrate, an embryo 

 escapes which perforates the gastric wall and settles in the numerous 

 organs, becoming encysted and losing the hooks ; thus forming 

 the " vesicular worm,'' or cystieercus. If this is introduced by any 

 kind of mechanism into the digestive canal of a host favorable to 

 its development, its scolex (head) becomes free as a result of the 

 digestion of the vesicle ; by means of its hooks it attaches itself to 

 the intestinal mucous membrane, and is developed, producing a 

 new colony. 



The knowledge of the transformations of ribbon-worms, estab- 

 lishing this capital fact, that the cysticerci form but a preliminary 

 stage of the tœnias, is due to the experimental researches of Van 

 Beneden, Kiichenmeister, V. Siebold, Leuckart, Haubner, and a 

 few others. 



The opinion of Mégnin,^ according to which the taenias armés 

 would only represent a stage of development of the taenias înerme, 

 has been denied by various authors (Moniez and Railliet ; Ziirn). 

 Mègnin affirms that the tsenias armés and tsenias inerme are pro- 

 duced by the same cystic larva. The Tcenia perfoliata of the horse, 

 for instance, would not be anything else than the Tœnîa JEchino- 

 coccus of the dog arrived at its last period of evolution. 



Anatomical lesions of the intestinal mucous membrane 

 produced by ribbon-worms. When the worms are not numer- 

 ous, the alterations frequently are but slightly marked, they are 

 catarrhal only. In other cases, on the contrary, we find intense 

 inflammatory lesions. On the intestinal mucous membrane of the 

 dog, Schieferdecker has detected regular tunnels in each of which 

 was located a cucumerine taenia. These canals were formed at the 

 expense of hypertrophied intestinal villi encysting the worm by 



Ï Mégnin : Bullet. Soc. cent. Vet., 1879. 



