THE TAPEWORM LARV.E 



201 



develop in almost any mammal to which they find access. The hog, 

 however, is the most common host, and, from the point of view of pxjbhc 

 health, the most important. 



As has been noted, the cysticercus of Taenia solium (Cysticercus cel- 

 lulosce) is a more dangerous parasite than that of T. saginata, as it may 

 lodge in organs such as the brain or eye with serious consequences. 

 Man can readily become a victim by auto-infection from his own armed 

 tapeworm, the eggs of which may reach his stomach by way of the 

 pyloris, or in being conveyed to the mouth by unclean fingers. By the 

 latter means, moustache twirlers and nail biters are especially exposed. 



Fortunately, the United States is favored by the rarity of the pork 

 tapeworm and consequently its cysts. Pig measles is most prevalent in 



Fig. 112. — Stages in tapeworm larval development: a, six-hooked larva 

 (hexaeanth or onchosphere) of Tsenia solium; b, cystic stage of same; c, same 

 with head evaginated; d, ciliated larva of Diphyllobothrium latum; e, plero- 

 cercoid of same — all enlarged (after Boas, by Kirkaldy and Pollard, from 

 Leuckart) . 



districts of foreign coimtries where bad hygienic conditions prevail; 

 where pigs are kept near dwellings, and their flesh is eaten raw or im- 

 perfectly cooked, conjoined with the practice of depositing human 

 excrement in the open or spreading it upon the fields as fertihzer. In 

 countries where sanitary control is of a more advanced standard the 

 prevalence of the pork tapeworm has been greatly reduced. 



Location and Appearance. — The muscles most often invaded by the 

 cysts are those of the tongue, neck, and shoulder, then, in order of 

 frequency, the intercostals, abdominal, psoas, the muscles of the thigh, 

 and those of the posterior vertebral region. Organs less often infested 

 are the liver, kidneys, heart, lungs, brain and eye. 



While the cysts may be scattered and few in number, they are, on 

 the other hand, sometimes present in certain locations in enormous 

 numbers. Kuchenmeister in one case found one hundred and thirty- 



