MAN'S FIGHT FOR SURVIVAL 619 



where the Paris green treatment had been used have almost com- 

 pletely eliminated malaria, while in towns only a few miles away 

 where no such treatment was used, four fifths of the inhabitants 

 contracted the disease in a single season. 



Yellow Fever and Its Relation to Insect Vectors 



Although we do not think of yellow fever as being an important 

 disease today, it was not more than a century and a half ago that it 

 played a very important part in the health of this country. As late 

 as 1878, the disease ravaged the Mississippi Valley, where in 34 cities 

 there were nearly 70,000 cases and over 16,000 deaths. 



The story of the conquest of yellow fever is one of the most thrilling 

 in medical annals. After the Spanish-American War, when yellow 

 fever was so prevalent in Havana, a military commission consisting 

 of Major Walter Reed, James Carroll, A. Agramonte, and Jesse 

 Lazear was established to investigate the control of the disease. 

 After a series of experiments which resulted in the death of Dr. Lazear 

 and the severe illness of several army volunteers, the mosquito Aedes 

 was proven to be the carrier of this dread disease. Methods of pre- 

 vention adopted as a result of these experiments were almost im- 

 mediately successful in Cuba and in other parts of the world where 

 the disease had been endemic. Yellow fever has always been 

 limited to areas near the seacoast or along the banks of navigable 

 rivers. It is prevalent during hot seasons, but much less of a 

 menace in cold weather. Now that we know the relation of the 

 disease to its transmission by the mosquito Aedes some of these points 

 clear up. 



No one has yet seen the causal agent of the disease. In 1918 

 the Japanese parasitologist, Noguchi, working for the Rockefeller 

 Institute, found a spiral organism which he believed was the cause. 

 Later he lost his life on the Gold Coast of Africa while still seeking 

 the causal agent. It is now believed that the organism is not a 

 spirochete, but a filtrable virus. Even though the organism is not 

 known, the fact that the carrier is has made it possible practically to 

 eliminate the disease from areas where as late as 1900 it was endemic. 



Typhus 



Another disease closely connected with an insect carrier is typhus. 

 During the seventeenth and eighteenth centuries epidemics of this 

 disease were frequent in crowded and unsanitary areas, especially 



