452 YELL OW FE VER. 



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 in- 

 fected. From time to time serious outbreaks occur, during 

 which neighbouring 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 occasionally 

 the disease may remain in abeyance for many years and then 

 originate de novo. There is, therefore, reason to suspect 

 that the infective agent can exist for considerable periods 

 outside 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 " prevalent in yellow fever regions. This would ex- 

 plain the degree of immunity which is shewn during a 

 serious epidemic by the older immigrants. 



Great variations are observed in the clinical types under 

 which the disease presents itself. Usually after two to four 

 days' incubation a sudden onset in the form of a rigor 

 occurs. The temperature rises to 104 F. to 105 F. 

 The person is livid, with outstanding bloodshot eyes. 

 There is great prostration, 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 im- 

 provement 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 



