240 THE TAPEWORMS 



occupies practically the whole segment, while nearly all the other 

 organs degenerate (Fig. 88). 



A man infested by a beef tapeworm expels several hundred 

 proglottids a month, each one gorged with many thousands of 

 eggs. Fortunately the majority of these never get an opportunity 

 to develop further but it is easy to see how some of the eggs may 

 reach their intermediate hosts, cattle, if the people who harbor 

 the worms are at all careless. Disseminated by rain water, 

 washed by streams into drinking troughs, carried about on the 

 feet of flies, adhering to the heel of a boot, and in many other 

 ways the eggs passed with the faeces may be transferred to the 

 grass or water eaten by cattle. In India, where this tapeworm 

 is common, cattle are said to devour human excrement if they 

 have access to it. 



When eaten by cattle or other ungulates, as the pronghorn 

 antelope, giraffe and llamas, the six-hooked embryos (Fig. 85) 

 escape from the eggs and migrate into the muscles of the new 

 host, attacking especially the muscles of mastication. Here in the 

 course of from three to six weeks they grow into bladderworms, 

 Cysticercus bovis, about one-third of an inch in length. They are 

 grayish white in color with a little yellow spot where the head is 

 invaginated. The fact that the cysts lack any marked contrast 

 to the muscle tissue, and if not very numerous may be obscured 

 by it, causes them to be overlooked frequently. If present they 

 can usually be found most readily in the muscles of mastication 

 or in the heart; these are the portions of the carcass regularly 

 examined in meat inspection. Beef which contains bladder- 

 worms is said to be " measly." 



Infection of man results, of course, from eating measly beef 

 which is raw or only partially cooked. In Abyssinia the Moham- 

 medans, who are forbidden by religious law to eat raw meat, are 

 practically free from tapeworm infection, whereas practically 

 all the non-Mohammedans are infected. The ripe proglottids 

 begin to appear in the faeces, several at a time, in the course of 

 two or three months after infection, and may continue to be 

 developed for years. 



Pork Tapeworm. Common in some parts of the world, but 

 very rare in the United States, is the species Tcenia solium, 

 which passes its bladderworm stage in hogs. Wherever raw or 

 imperfectly cooked pork is eaten, infection with this tapeworm is 



