When the Second World War moved into the tropics, it suddenly raised 

 serious health problems for the armies of countries that had considered them- 

 selves quite finished with malaria and yellow fever and other tropical diseases. 

 When the Japanese captured the Dutch East Indies, the supply of quinin was 

 cut off from the United Nations. It was out of the question to drain swamps 

 and fill in marshes in the Philippines: Corregidor and Bataan submitted to 

 malaria quite as much as to the bombs and machine guns of the enemy. Since 

 then, however, chemists and physiologists have developed a substitute for 

 quinin, starting with a German product, "atrabine", which we are able to make 

 in our own laboratories. Atrabine is not as effective as quinin in curing 

 malaria, but has been helpful as a preventive, especially when combined with 

 quinin. In the meantime a very satisfactory vaccine to meet the yellow- 

 fever menace has been developed through researches of scientists supported 

 by the Rockefeller Foundation. 



Rats, Plagues and Fleas The plague has spread from the Orient, and 

 at various times cases have appeared at several ports in the United States. 

 In dealing with this danger, efforts are directed toward killing rats and fleas 

 rather than toward killing bacteria. A ship coming from an affected port is 

 thoroughly fumigated to kill the fleas and rats (see illustration, p. 628). A 

 search is made for hiding-places in which rats may be concealed. In California 

 the ground-squirrels had become infected with the plague bacillus early in this 

 century. Systematic patrols had to be established to catch rats and ground- 

 squirrels, which are regularly examined for possible infection. To protect 

 human life it is necessary either to exterminate some of our neighbors or to see 

 that they keep well. We can hardly undertake to protect the rats and other 

 rodents from plague; we can protect ourselves only by exterminating the rats. 



Lice and Ticks Trench fever is seldom fatal, but it caused a great deal 

 of suffering and incapacity among soldiers during the First World War, Volun- 

 teers from the ambulance and field-hospital units allowed themselves to be 

 infected with the blood of patients. Other volunteers, who allowed them- 

 selves to be bitten by Hce taken from the bodies of patients, developed the 

 disease. Still others, however, living under exactly the same conditions, but 

 bitten by lice from healthy men, remained unaffected. These experiments 

 showed that the infection is carried by the louse. By "delousing" all the 

 men, including officers, the disease was brought under control. 



In the past there were frequent epidemics of typhus and of related diseases 

 among crowded people or where it was difficult to keep clean. In these epi- 

 demics the mortality was often very high — from 20 to nearly 50 per cent. 

 All these diseases are now known to be caused by similar microbes, which are 

 parasitic upon rats and other small mammals, as well as upon man. And they 

 are transmitted by insects — chiefly the body louse. 



Several diseases resemble typhus in their outward symptoms. The group 



625 



