WORMS 



167 



Trichina. Round worms are another class of parasites, of which 

 the " vinegar eel " and the intestinal pin worms are comparatively 

 harmless forms. The pork worm (trichina) of this same class may 

 cause serious illness or death. These worms pass their first stage 

 in the pig, dog, cat, ox, or horse, where they bore into the muscles, 

 surround themselves with a coating (cyst), and remain alive but 

 inactive. If such flesh be eaten when improperly cooked the cyst 

 is dissolved, the worms develop, 

 bore through the tissues 

 again, and produce the painful 

 and often fatal disease known 

 as trichinosis. The tapeworm 

 is large; usually only one is 

 present and it does its chief 

 harm by absorbing food 

 needed to nourish the body. 

 The trichina, on the other 

 hand, is microscopic in size, 

 vastly numerous, and pro- 

 duces acute disease by penetra- 

 tion of the tissues. Careful in- 

 spection and thorough cooking 



Fig. 54. Section through the skin 

 of a dog two hours after it has been 

 infected with the Old World hook- 

 worm. (Greatly enlarged; after 

 Wilder.) From Kellogg and Doane. 



of meats are lessons to be learned 

 from the above life histories. 



Hookworm. The hookworm is another parasite, found in the 

 southern states, which attacks man by way of the feet and thence 

 by way of the veins, lungs, and throat, penetrates to the intestine, 

 where it absorbs food and causes loss of blood. This lowers its 

 victim's strength and produces the characteristic laziness of the 

 " poor whites " of the South. Almost all animals, from clams and 

 insects to cattle and man, are subject to the attacks of parasitic 

 worms. The hookworm alone costs this country about twenty 

 million dollars ($20,000,000) per year, in loss of labor due to its 

 effect on health. 



Note: The " horsehair snake " which you frequently find in 

 ponds and streams has nothing to do with a horsehair, nor is it a 



