THE HOOKWORM 



495 



/ 



the human 

 . excretcc 

 infects soil 



vorm enters 

 skin from, 

 dirt betveeii 

 the. toes 



Demonstration 7. Use a microscopic slide to show hookworm. Why 

 is it called " hookworm " ? 



The hookworm. The account of the discovery by Dr. C. W. 

 Stiles of the Bureau of Animal Industry, that the laziness and shift- 

 lessness of the " poor whites " of the South is partly due to a para- 

 site called the hookworm, reads like a fairy tale. 



The people, largely farmers, become infected with a larval stage 

 of the hookworm, which develops in moist earth. It enters the 

 body usually through a break in the skin of the feet, for adults 

 and children alike, in certain localities where the disease is com- 

 mon, go barefoot to a considerable extent. 



A complicated journey from the skin to the intestine now follows. 

 The larvae pass through the veins to the heart, from there to the 

 lungs, where they bore into the air passages, and eventually reach 

 the intestine by way 

 of the throat. One 

 result of the injury to 

 the lungs is that many 

 persons thus infected 

 are subject to tuber- 

 culosis. The adult 

 hookworms, once in 

 the food tube, fasten 

 themselves to the 

 walls which they 

 puncture ; and then 

 they feed upon the 

 blood of their host. 

 The loss of blood 

 from this cause is 

 not sufficient to ac- 

 count for the blood- 



lessness of the person infected, but it has been discovered that the 

 hookworm pours out into the wound a poison which prevents the 

 blood from clotting rapidly ; hence a considerable loss of blood 

 occurs from the wound after the hookworm has finished its meal 

 and gone to another part of the intestine. 



fiora stomach 

 to intestines 

 hooKs oix-fe 

 the"NVall 



\ 



is 



svttllovect 



Carried 

 to heart 



\ 



to vessels 

 in lungs 



breaks 

 lttto the 

 air -sacs 



up through 

 Vmdpipe 

 to the 

 mouth 



Explain, from the diagram, how one may become infected 

 with hookworm. 



