YELLOW FEVER. 455 



during life or post mortem. Inoculate a number of agar tubes 

 by successive strokes and incubate at 37 C. Film preparations 

 should also be made from the spleen pulp and stained with 

 carbol-thionin-blue or diluted carbol-fuchsin (i : 10). 



YELLOW FEVER. 



Yellow fever is an infectious disease which is endemic in the 

 West Indies, in Brazil, in Sierra Leone, and the adjacent parts 

 of West Africa, though it is probable that it was from the first- 

 named region that the others were originally infected. From 

 time to time serious outbreaks occur, during which neighbour- 

 ing countries also suffer, and the disease may be carried to other 

 parts of the world. In this way epidemics have occurred in the 

 United States, in Spain, and even in England, infection usually 

 being carried by cases occurring among the crews of ships. In 

 the parts where it is endemic, though usually a few cases may 

 occur from time to time, there is some evidence that occasion- 

 ally the disease may remain in abeyance for many years and 

 then originate de nova. There is, therefore, reason to suspect 

 that the infective agent can exist for considerable periods out- 

 side the human body. It is possible, however, that continuity 

 may be maintained by the occurrence of a mild type of the 

 disease which may be grouped with the " bilious fevers " preva- 

 lent in yellow-fever regions. This would explain the degree of 

 immunity which is shown during a serious epidemic by the 

 older immigrants. 



Great variations are observed in the clinical types under 

 which the disease presents itself. Usually after from two to six 

 days' incubation a sudden onset in the form of a rigour occurs. 

 The temperature rises to 104- 105 F. The person is livid, with 

 outstanding bloodshot eyes. There are present great prostra- 

 tion, pain in the back, and vomiting, at first of mucus, later of 

 bile. The urine is diminished and contains albumin. About 

 the fifth day an apparent improvement takes place, and this 

 may lead on to recovery. Frequently, however, the remission, 

 which may last from a few hours to two days, is followed by 

 an aggravation of all the symptoms. The temperature rises, 

 jaundice is observed, haemorrhages occur from all the mucous 

 surfaces, causing, in the case of the stomach, the "black vomit" 



