THE INFECTIOUS DISEASES. 



273 



cutr.neous injection into a healthy individual of a small quantity of blood 

 drawn from a patient in the early stage of the disease. It has further- 

 more been shown by repeated and abundantly confirmed experiments 

 that yellow fever may be induced in a non-immune individual by the 

 bite of the mosquito Stegomyia which has previously bitten a patient 

 in an early stage of the disease. Practical sanitary procedures based 

 upon the hypothesis that this mosquito acts as an intermediate host in 

 which the (unknown) yellow-fever parasite passes one of its develop- 

 mental cycles, have furnished strong evidence that it is through the inter- 

 vention of this mosquito, and thus only, that the disease is conveyed. 

 For it has been possible, by the prevention of access of this mosquito to 

 yellow-fever patients through the use of netting and other precautionary 

 measures, practically to suppress the disease in Havana, where it was 

 formerly endemic, and to stifle epidemics elsewhere. ' It has been further 

 demonstrated in the most conclusive way that the infectious agent in 

 yellow fever is not conveyed directly through the air or by fomites. 2 



VARIOLA. (Smallpox.) 



Smallpox is an acute, readily communicable, infectious disease, es- 

 pecially characterized anatomically by an inflammation of the skin which 

 passes through a series of more or less distinctive phases of papule, vesi- 



m 



#>'-"" < T; 



%'l 

 f|.' | 



p ; ;..- .:: .:-..-. ;;: ff g 



! 



FIG. 1S8. A SMALLPOX VESICLE OF THE SKIN. 



cle, pustule, with a final drying of the exudate and necrotic tissue con- 

 stituting the crust. 



Various phases of the exanthem are used to designate forms of the 

 disease. 



1 For a summary of observations relating to the mosquito as an intermediary host 

 of the infectious organism in yellow fever, see Reed. Carroll, and Ayrqmonte, Phila, 

 Med. Jour., October 27th, 1900; also Jour Am. Med. Assn., February 16th, 1901; 

 Amer. Med., July 6th, 1901; Gmterus, Amer. Med., November 23d. 1901; Dvrfuim, 

 Thompson Yates' Laboratories Report, vol. iv.. 1901, p. 485; Reed and Carroll. Am. 

 Med., February 22d, 1902; also Carroll, Jour. Am. Med. Assn., May 23d. 1903. 



9 For a brief resume of the reasons for the belief that the mosquito is the sole agen' 

 in the conveyance of the infectious agent in yellow fever, see Carter. Bull of the Yel 

 low Fever Institute, No. 10, July, 1902, Bureau of Public Health and Marine Hospital 

 Service, U. S. A. For a description of the mosquito Stegomyia fasciata and modes of 

 prevention in yellow fever, see Reed and Carroll. Med. Rec.,' October 26th, 1901. For 

 the bearing of this subject upon quarantine regulations, see Doty, Med. Rec., October 

 26th, 1901. 



18 



