THE ECONOMIC IMPORTANCE OF ANIMALS 229 



lows, the larvae passing through the veins to the heart, from there 

 to the lungs ; here they bore into the air passages and eventually 

 work their way by way of the windpipe into the intestine. One 

 result of the injury of the lungs is that many thus infected are 

 subject to tuberculosis. The adult worms, once in the food tube, 

 fasten themselves and feed upon the blood of their host by punc- 

 turing the intestine wall. The loss of blood from this cause is 

 not sufficient to account for the bloodlessness of the person in- 

 fected, but it has been discovered that the hookworm pours out a 



A family suffering from hookworm. 



poison into the wound which prevents the blood from clotting 

 rapidly (see page 315) ; hence a considerable loss of blood occurs 

 from the wound after the worm has finished its meal and gone to 

 another part of the intestine. 



The cure of the disease is very easy; thymol is given, which 

 weakens the hold of the worm, this being followed by 

 Epsom salts. For years a large area in the South undoubtedly 

 has been retarded in its development by this parasite ; hundreds of 

 millions of dollars and thousands of lives have been needlessly 

 sacrificed. 



