SPIROCHAETES 



29 



The yellow-fever commission sent by the United States to 

 Cuba in 1900 was perhaps the best result of the Cuban war. 

 The commission consisted of Dr. Walter Reed, Dr. James Car- 

 roll, Dr. Jesse Lazear, and Dr. A. Agramonte. Dr. Lazear died 



Fig. 16— TREPONEMA GALLINARUM 



A spirochaete which causes relapsing fever in ducks and other fowls. Similar microscopic 

 snakes cause relapsing fever in humans. The elliptical-shaped bodies are blood cells 



From a photomicrograph by the author 



Magnification, 1500 



of yellow fever and Dr. Carroll contracted it and lay at the 

 point of death for several days, but finally recovered. They 

 established the fact that exposures to the disease or to soiled 

 articles, bedding, etc., from its victims, are without effect, but 

 the bite of a single infected mosquito, even under the most sani- 

 tary conditions, produces the disease. They learned that when a 

 mosquito has bitten a yellow fever victim and has become in- 

 fected, it cannot transmit the disease for a period of twelve days 

 — in other words a period of development in the mosquito is 

 necessary. They learned that a human being, bitten by an infected 

 mosquito, will infect another mosquito only during the first three 



