334 BIOLOGY AND HUMAN LIFE 



The secondary stage of the tapeworm is sometimes injurious to the 

 other host also, forming what is called a bladder worm. Sometimes 

 the human organism serves as the secondary host, and in this case the 

 bladder worm may cause serious destruction of some tissue or organ. 



250. Trichina. A widespread parasite belonging to the round- 

 worm group is Trichina, which embeds itself in the muscles 

 of the host, a mammal. A related parasite that produces 

 trichinosis in human beings is called Trichinella, and it usually 

 alternates between man and pig. Pork infested with the tri- 

 china is called measly pork ; it should not be eaten. When 



the number of cysts 

 is very small, a super- 

 Fig. 157. The American hookworm ~^ ^^^^1 inspection may 

 (Necator americanus) ^^^ reveal them. It 



^, , , -1 ^, . ^ -.1, ♦!, is always best, there- 



The hookworm is large enough to be seen with the -^ ' 



naked eye and looks like a small bit of thin white fore, tO COOk pork SO 



thread. It multiplies very rapidly in the intestine ^^ ^^ destroy the tri- 



and encysted eggs find their way to the exterior with ^ -^ 



the feces of the host. In the sandy soil the embryo chinella, rather than 



emerges. The infection of human beings is brought . take a chance of 

 about by contact with the contaminated soil 



becoming infected. 



251. The hookworm. Early in this century investigations 

 conducted under the direction of Dr. Charles W. Stiles of the 

 United States Public Health Service disclosed the fact that the 

 "poor whites" of our Southern states were suffering from an 

 intestinal parasite, the hookworm, which depleted their energies, 

 emotional and intellectual as well as physical (see Fig. 157). 

 The announcement of this discovery was at first ridiculed, be- 

 cause nobody would take the ''laziness germ" seriously. Self- 

 righteous people said, "Laziness is laziness, and that's all there 

 is to it — no use blaming sickness or worms for being lazy." Yet 

 the fact remains that with the removal of the parasite these 

 white folks appear to be equal to the best stocks in the country. 



In parts of some Southern states most of the children and 

 many of the adults go about barefooted, and children play on 

 the ground. In some districts almost every inhabitant was in- 

 fected when the investigations were made. Now we know that 



