466 Biology in America 



by way of the hair follicles, sweat ducts, etc. To follow the 

 further course of the larvae he placed some of them on the 

 skin of a number of dogs which were killed and examined at 

 various intervals. In this way he worked out the entire 

 course of the larvae from the skin to their final resting place 

 in the intestine." 14 



Where a number of poor and ignorant miners were col- 

 lected in narrow underground quarters, as in the building of 

 a tunnel, with no proper arrangements for the disposal 

 of bodily wastes, it is plain that the most elementary rules 

 of health would be disregarded and that filth would abound. 



The hookworm derives its name from the slightly bent or 

 hooked anterior end. In the mouth are four hooks and two 

 conical teeth by means of which it attaches itself to the mu- 

 cous membrane of the intestinal wall. Here it is said to live 

 for several years, during which time it produces an enor- 

 mous number of eggs. If these chance to be deposited in a 

 moist place, as in the pools of water in a mine or tunnel, they 

 hatch into larvas which live in the water or moist earth until 

 they meet the bare skin, usually of the feet, of another vic- 

 tim. They then bore through the skin into the blood ves- 

 sels where they are carried by the blood stream to the heart 

 and finally to the lungs. Here they leave the circulation, 

 enter the lungs, and crawl into the bronchial tubes, up which 

 they crawl to the' throat and thus reach the oasophagus. From 

 here they pass through the stomach to the intestine. The 

 hookworm may also reach the intestine directly in unwashed 

 fruit or raw vegetables. 



Knowledge of hookworm disease and the part it plays in 

 deteriorating so large a proportion of our southern popula- 

 tion is mainly due to Dr. Charles W. Stiles, the parasitolo- 

 gist of the U. S. Public Health Service. Stiles has studied 

 the disease extensively in the South and found the cause to 

 be the same as in Europe although the American worm is 

 somewhat different from its European cousin. Stiles' re- 

 searches, aided by the liberality of the Rockefeller Founda- 

 tion, and by the activity of state boards of health throughout 

 the South, have made widely known the cause, and means of 

 prevention and cure of the disease. The abolition of the 

 unsanitary privy on the one hand, and thymol and epsom 

 salts on the other, will rid the world of a scourge infesting 

 an area in which live about 1,000,000,000 people, or more than 

 half the total poulation of the world, with an infection rate 

 in some countries as high as ninety per cent among the labgr- 



a * Keese, ' ' Economic Zoology, ' ' p. 35. By permission of P. Blakiston 's 

 Son and Company. 



