CHAPTER XXX 



ANIMAL PARASITES AND VERMIN 



Although in no sense related to bacteria, we venture 

 to include a few words concerning some of the commoner 

 animal parasites of man, because, in most instances, the 

 methods of guarding against such infections is similar 

 to those employed in guarding against bacterial infec- 

 tion. 



Tapeworms. — ^These have a double cycle of life, exist- 

 ing in man as the common tapeworm familiar to all, 

 and in the flesh of cattle or hogs in the form of tiny 

 * 'bladder worms.'' The common tapeworm of North 

 America is found in the meat of cattle, and, while it is 

 readily killed by cooking the meat, is liable to infect 

 persons who eat raw meat. 



Sometimes it happens that man accidentally takes 

 into his stomach the ripe ova (eggs) of a tapeworm. 

 When this happens he is liable to become the interme- 

 diate host, the part usually played by the pig or by 

 cattle. A disease known as "echinococcus disease" is 

 caused by man accidentally swallowing the ripe ova of a 

 tapeworm ordinarily infecting dogs. 



Trichina. — This is a parasite found in the flesh of hogs 

 and transmissible to man. From the intestinal canal of 

 man these tiny worms pass into the muscles, where they 

 lodge and give rise to considerable pain and weakness. 

 Trichiniasis, as the disease is called, is uncommon in 



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