MICROBIAL DISEASES OF MAN AND DOMES-TIC ANIMALS 82 1 



t 

 from a t)rphus fever patient. The virus may be transferred from one 

 monkey to another indefinitely. In monkeys recovery from severe 

 attack produces a firm immunity. No microorganism has been dis- 

 covered which can be regarded as the cause of the disease. Attempts 

 to pass the virus through filters have been unsuccessful with the possible 

 exception of certain experiments by NicoUe. The virus is destroyed 

 by heating from 50 to 55°. 



Yellow Fever* 



Yellow fever is an acute infectious, non-contagious disease of man 

 which is seen in tropical and sub-tropical countries, particularly the 

 West Indies, South America, and the west coast of Africa. The most 

 notable symptoms of the disease are fever, jaundice, and haemorrhages 

 from the mucous membranes, this latter resulting in severe cases in 

 what is known as "Black Vomit," which consists chiefly of extravasated 

 blood which has been changed to a brown or black color by the action 

 of the gastric juice. 



Prior to the brilliant researches of Walter Reed and his associates 

 on the United States Army Commission in the year 1900, it was 

 generally believed that yellow fever was contagious, and that the 

 disease was transmitted directly from infected to non-infected in- 

 dividuals, and furthermore that the clothing, bedding, and all materials 

 which came into contact with the infected subject were capable of 

 transmitting the disease. Reed and his associates, during the American 

 occupation of Cuba, secured a number of volunteer subjects to serve 

 the Commission in its studies. This Commission demonstrated posi- 

 tively that yellow fever could not be transmitted to man in any other 

 way than by the bite of a particular mosquito, A'eies (Stegomyia) 

 cdopus (Meigen). These mosquitoes were allowed to bite patients 

 suffering from yellow fever at different stages of the disease. Sub- 

 sequently these same mosquitoes were allowed to bite healthy men 

 at different periods of time following their application to the infected 

 individual. It was proved that the mosquito, in order to be capable of 

 conveying the disease, must bite an infected individual during the first 

 three days of the fever and at least twelve days must elapse thereafter 

 before the mosquito is capable of transmitting the disease to a sus- 

 ceptible individual. 



* Prepared by M, I>QTset,J[, 



