PARASITES 369 



The fully developed larvae may be found coiled up in the muscles of the 

 prothorax and limbs. Infection occurs in the primary host by the ingestion 

 of the infected insects. 



Fibiger (16) in Denmark has reported extensively on this parasite in 

 relation to its induction of neoplasms in the fundus of the stomach of the 

 mouse and rat and in the tongue of the rat. He describes these neoplasms 

 as possessing exactly the same histological structure as epitheliomata in man 

 and animals. 



Trichinella spiralis (owen, 1835). — Also known as Trichina spiralis. 

 The "trichina worm," well-known as the organism which causes trichinosis, 

 is a parasite of hogs, rats, mice, and other mammals, including man. The 

 adults live in the small intestine and the larvae in the muscle tissue. 



The adult is a small worm with the body somewhat tapering anteriorly. 

 The male is from 1.4 to 1.6 mm. long, and the female from 3 to 4 mm. The 

 adult male and female copulate in the intestine of the host, after which the 

 female burrows into the mucosa of the intestine. The female is viviparous, 

 the larvae being deposited in the lymph spaces. The embryos make their 

 way to the voluntary muscle and into the sarcolemma, developing into the 

 infective larvae which assume the spiral form within the lemon-shaped cyst. 

 Muscles with the richest blood supply are said to be most heavily para- 

 sitized. Infection occurs by eating muscle tissue containing these infective 

 larvae. 



It is highly possible that trichinosis could become a serious disease among 

 laboratory mice if the infestation were permitted to become intense. How- 

 ever, under usual laboratory conditions where few mice are kept in the same 

 cage and where animals are seldom permitted to die in the cages and be eaten 

 by their mates, there is slight chance for intense infection. 



Other nematodes of the mouse. — The following are species described for 

 the mouse but of less importance than the above forms. 



Capillaria bacillata (eberth, 1863). — Reported from the oesophagus of 

 the mouse. 



Ollulanus tricuspis leuckart, 1865. — Adults live in the gastric mucosa 

 of the cat. Larvae develop in the musculature and connective tissue of the 

 mouse. 



Gongylonema musculi (rudolphi, 1819). — Reported from the liver and 

 on the external walls of the stomach. 



Heterakis spumosa Schneider, 1866. — Usually reported from the 

 caecum of the rat, but Harkema (18) found it in the house mouse. 



For further description of these species see Hall (17). 



