MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 875 



in Tunis, and Anderson and Goldberger, and Ricketts and Wilder 

 working in Mexico, showed that typhus is communicated from man 

 to man by means of the body louse (Pediculus vestimenti), and that 

 the disease is not contagious in the ordinary sense of the word. Nicolle 

 states that after biting a typhus fever patient the louse cannot convey 

 the infection until the fourth day thereafter and that it loses this power 

 after the seventh day. This indicates a similarity between the micro- 

 organisms causing yellow fever, malaria and typhus. The disease may 

 be communicated to monkeys by subcutaneous inoculations of blood 

 from a typhus fever patient. The virus may be transferred from one 

 monkey to another indefinitely. In monkeys recovery from severe 

 attack produces a firm immunity. Plotz* has isolated a small Gram- 

 positive bacillus which he believes to be the cause of the disease. At- 

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

 possible exception of certain experiments by Nicolle. The virus is 

 destroyed by heating from 50 to 55. 



YELLOW FEVER f 



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 was not transmitted to man in any other 



* Plotz, Jour. Inf. Dis., July, 191 5- 

 t Prepared by M. Dorset. 



