76 DISEASES OF THE DIGESTIVE APPARATUS. 



meats that separate from the parent parasite when they are fully 

 developed and are carried out among the feces. Each segment is 

 complete in itself, haviug both male and female genital organs. 

 This order are hermaphrodites, and are peculiar from the fact that, 

 they produce the germs of new nursing mothers in the shape of eggs, 

 while the nurse remains sexless. The ripe segments (proglottides) 

 are soon detached and passed either into manure or in water wliere 

 there are aquatic plants. They then go through several forms 

 and are taken up by a new host. The eggs are covered with a 

 hard, tough shell, inside of which is a six-hooked embryo. If 

 this egg is taken into the stomach, the acid gastric juice dissolves 

 the shell, the embryo is liberated, and immediately fastens the 

 hooks into the mucous membrane, and from there perforate into 

 the connective tissue of some of the adjacent organs, wliere they 

 lose their hooks and form a sac-like cyst. These contain fluid, 

 and are termed bladder-worms. These cysts form bladder-like 

 excrescences on their sides, which develop and increase in size, and 

 are named, from their shape and size, coenurus when empty, and 

 cysticercus or cysticercoid when they contain fluid. In each of 

 these bladders we find the individual taenia head, furnished with 

 the ring of hooks and the sucking cups. These bladders divide 

 and subdivide into numerous daughter-cysts or breeding buds, all 

 of which produce the little heads of the taenia. 

 Fig. 22. jijjjg jg frequently seen in the echinococcus, where- 



enormous masses are formed. If any domestic 

 animal gets one of these ripe bladder-worms into 

 the stomach, the gastric juice dissolves its cover- 

 ing and it finds its way to the duodenum, when 

 it fastens itself by means of its hooks and suck- 

 ing apparatus and instantly becomes a breeding 

 parasite. 



The anatomical structure of the cestodes (Figs. 

 22, 23, and 24) is very simple. The body is di- 

 vided into two layers, an external and an inner 



Uteras of the taenia • t .. i i j j o i i 



coenurus (enlarged), covermg. in the latter we find the sexual organs. 

 The external layer is chiefly muscular, and con- 

 tain also a mass of calcareous nodules that replace the defective 

 bony structure of the cestodes. The surface of the head is covered 

 with a skin or cuticle from which the Iiooks originate. The- 



