THE WORM-LIKE ANIMALS 845 



Suppose one half of these are females, each able to produce 

 1000 young worms, and four million encysted worms might 

 be the result. Thus, at this rate, 100 pounds of pork might 

 contain enough cysts to develop 64 billions of encysted worms, 

 or 160 million for each of 400 persons who might eat the pork. 

 And this is not the whole story, for a female trichina may 

 live in the human intestine and frequently give birth to as 

 many as 1000 young. It is easy from such figures to see how 

 a single infected pig could have caused so much trouble. 



There is no way to stop the worms when once they get 

 into the human intestine. If the infected individual does 

 not soon die from the inflammation caused by the encysting 

 in the muscles, the cysts soon become hardened and there is 

 no more danger to the patient. Prevention is very simple; 

 namely, eat no pork which is not well cooked. Government 

 inspectors in the United States and other countries examine 

 meats at the great packing houses and slaughter houses, and 

 condemn as unfit for human food all meat found to have 

 trichinae. Inspection is not difficult, for if the parasites are 

 present in a pig, they are likely to be so abundant that a small 

 piece of lean meat (muscle) examined with a microscope 

 will reveal the trichinae. However, the parasites have 

 been sometimes overlooked by expert inspectors. 



The above account has not explained how pigs get infected. 

 Since they do not eat human flesh, they must get the para- 

 sites from some other animal. Trichinae are found in rats, 

 and it is well known that pigs will eat dead rats. Also, 

 pigs might eat scraps of pork thrown out in garbage. 



298. The Horsehair Worm. In some rural districts, it 

 is still believed that a long, thread-like worm, looking not 

 unlike a long hair from a horse's mane or tail, and found 

 wriggling in pools of water, has developed from horsehairs 

 which have happened to fall into the water. Hence the 

 names " horsehair worm " or " horsehair snake." The be- 

 lief seems to have been originated, and is still perpetuated, 



