PARASITES OF ANIMALS. 119 



eating slaughter-house offal. It is possible, also, to infect 

 hogs and other animals by means of the mature female 

 Trichince that have been discharged from the intestines of 

 men or animals, before all the young worms contained in their 

 uteri have been born. Therefore hogs may obtain this, as 

 well as the Iarva3 of the tape-worm of man and many other 

 parasites, by being kept in places where they have access to 

 manure, as is too often the case. Cats, rats, mice, rabbits, 

 Guinea-pigs, young dogs, and various other animals may be 

 infected, but adult dogs, like old hogs, are not nearly so likely 

 to become infected as the young. Although lambs, calves, 

 and horses may be infected by forcing them to eat trichinous 

 meat, it is probable that they seldom or never become infected 

 naturally. 



Trichocephalus dispar Rudolphi. Figure 77. 

 This is a small round-worm, living in the human intestine, 

 and remarkable for its long, very slender, filiform neck, which 

 Figure 77. * s about two-thirds of the entire length. The 

 male grows to the length of one inch and a 

 half, and the female to two inches. The sur- 

 face of the body appears smooth to the naked 

 eye, but when magnified, a longitudinal band of 

 minute, wart-like papillae is seen on one side. 

 The male has the posterior end of the body 

 spirally curved, with a single spicule, which is 

 emitted from the extremity of the body, and is 

 enclosed in. a short, tubular sheath, that is cov- 

 ered with minute recurved spinules. The female 

 has the posterior end of the body nearly straight 

 and bluntly pointed (Figure 77). The genital 

 orifice is situated at the origin of the neck. The eggs are 

 elliptical, with a small projection at each end, and are -&G to 

 ?fa of an inch long. They are discharged from the human in- 

 testine before the contained embryos are fully developed. If 

 kept in water for six months or more they hatch, liberat- 

 ing a minute embryo 3^ of an inch long, which tapers 

 from behind toward the head. 



Figure 7 '7. Trichocephalus dispar,' a, female, natural size ; b, posterior end, en- 

 larged. From Guerin. 



