CHAPTER XVII 



THE TAPEWORM LARV.E 



Certain tapeworms are to be considered as to their pathogenicity 

 from two important points of view. They are not only parasites in their 

 adult state in the intestines of domestic carnivores and man, but, in the 

 larval stage live as somatic parasites in animals used as food by man 

 and it may be in man himself. Depending. much upon their numbers 

 and form of cyst, these cause no disturbance to their host, or, through 

 their growth, pressure, and inaccessibility, may constitute a menace to 

 health far more serious than that of the adult worms in the intestines. 



Three forms of cestode larvae are principally concerned in this connec- 

 tion, — cysticercus (Fig. 107), ccenurus (Fig. 114), and echinococcus 

 (Fig. 117). A brief synoptical arrangement of these, including the 

 cysticercoid and plerocercoid, follows: 



I. Larva having a caudal vesicle. 



A. Larva of large size. Liquid in caudal 

 vesicle abundant. Found in tissues 

 and closed cavities of Herbivora and 

 Omnivora, occasionally in Carnivora. 

 1. Vesicle and head single, i. e., cyst 

 monosomatic and monocephalic. 



2. Vesicles multiple, each having a 

 single head, i. e., polysomatic and 

 monocephalic. 



3. Vesicles multiple, having many 

 heads in each, i. e., polysomatic 

 and polycephalic. 



Cystic 



Cysticercus 



{Cysticercus 

 pisiformis, larva of 

 Twnia pisiformis) 



Multiceps 



(Multiceps multiceps, 

 larva of M. multiceps) 



Echinococcus 



{Echinococcus granu- 

 losus, larva of E. 

 granulosus) 



