YELLOW FEVER 185 



of " calm " during which the temperature is near normal but the 

 pulse very slow. By the third day the skin usually becomes a 

 characteristic yellow color, which, as the disease progresses, 

 changes to a deep coffee brown. A striking but not invariable 

 symptom, and one of ill omen, is the " black vomit," a gushing 

 up through the oesophagus of a coffee-colored or even black fluid, 

 consisting largely of fragments of red blood corpuscles and freed 

 haemoglobin, and sometimes even pure blood. The period of 

 " calm " may lead to recovery in a few days or there may be a 

 second fever which lasts irregularly for a longer time than the 

 first. 



Yellow fever is a very fatal disease. During the French 

 operations at Panama relay after relay of laborers were stricken 

 with the yellow plague and were turned loose to die without 

 mercy or help, to be replaced by a new set. Not only the laborers 

 but the engineers, nurses and others were stricken down. One 

 vessel is reported to have brought over 18 young French engi- 

 neers, all but one of whom died of yellow fever within a month 

 after their arrival. 



Fortunately yellow fever gives a permanent immunity after 

 one attack has been successfully withstood. In children the 

 disease is often very mild so that it is frequently not even recog- 

 nized, yet the immunity it gives is permanent. Natural im- 

 munity is unknown in any race, sex or age, though the negroes 

 suffer less from the disease and have a much lower per cent of 

 mortality than the whites. 



Treatment and Prevention. — There is no special drug so 

 far known which acts as a specific poison against the yellow fever 

 parasites. Careful nursing and perfect hygienic conditions are 

 the best remedies we have. The eradication of yellow fever 

 consists simply in the extermination of the yellow fever mos- 

 quito, Aedes calopus. The habits of the insect, as described on 

 p. 444, are such that it is not difficult to combat and successful 

 campaigns against it, with a resultant obliteration of yellow 

 fever, have been made in many places. In Louisiana the anti- 

 mosquito campaigns have been so effective that Aedes calopus, 

 once one of the most abundant pests, is now nearly exterminated 

 in all parts of the State, and there has been no endemic or epi- 

 demic yellow fever since 1905. Panama, Havana, Rio de Ja- 

 niero, and recently Manaos and Yquitos, are conspicuous examples 



