PARASITOLOGY. 193 



Canina is the biting louse (Trichodectes Latus) and 

 the flea (Pulex Serraticeps), These insect parasites 

 become infested while procuring food which is con- 

 taminated ; the minute embryo is liberated in the di- 

 gestive tract, migrates to the abdominal cavity and 

 there forms a cyst known as the cryptocystis tricho= 

 dectis (if formed in the louse) or cryptocystis 

 pulecidae (if formed in the flea). The dog, by biting 

 itself to relieve the irritation caused by these insects, 

 gets them in its mouth ; thus the larva, which consists 

 of the scolex or head, and neck, after being liberated 

 through digestion finds its way to the small intes- 

 tines, and attaching itself to the mucous membrane 

 becomes fully developed in about five weeks. 



Animals Infested. — The adult infests the dog ; 

 the larval or cystic form infests the flea and louse of 

 the dog. 



Symptoms. — 7reatme?it. — Same as in the preceding 

 species. 



Prophylaxis. — Keep dogs and kennels free from 

 fleas and lice ; in this way the chain of the life cycle 

 is broken. 



TAPEWORMS OF THE CAT. 



The tapeworms of the cat are armed ; the following 

 is the most common. 



Taenia Crassicollis. 



Distribution. — Found in the United States. 



Description. — The worm may reach the length of 

 five feet; the terminal segments are longer than wide; 

 the head is provided with four sucker discs and a 

 rostellum of from thirty to fifty booklets ; the neck 

 is thick and short. 



