YELLOW FEVER 401 



therefore the probable locality of the causal bacillus; whereas, as 

 Sanarelli pointed out, the B. icteroides must be sought for in the blood 

 and tissues, and not in the alimentary canal. But even thus the 

 difficulties are not wholly removed. For it happens that this 

 organism may only be found in comparatively small numbers, and 

 certainly at the beginning of the disease multiplies very little in 

 the human body. Its influence upon the body, too, appears to be 

 such that the tissues of a yellow fever patient become the hunting 

 ground of vast numbers of secondary infective bacteria. 



This bacillus (£. icteroides) may be obtained from the small 

 capillaries — in, say, the liver — by incubation at favourable tempera- 

 ture (37° C). It is a short bacillus with round ends, like B. coli. It is 

 motile, and possesses 4-8 flagella. It develops sufficiently well for all 

 practical purposes on the ordinary media. On agar at blood-heat it 

 grows well — a grey, iridescent, smooth layer, with regular margins ; 

 and on the same medium, at the temperature of the room, it 

 produces in twenty-four hours characteristic colonies not unlike drops 

 of milk. It grows on gelatine without liquefaction. The organism 

 is a facultative anaerobe, decolorised by Gram's method; ferments 

 sugar, but does not coagulate milk until after some weeks. It 

 appears strongly to resist drying. Direct sunlight kills it in seven 

 hours ; but it is said to be able to live for some time in sea water. 

 The organism can be isolated from the living patient as well as the 

 dead body.* 



Sanarelli has maintained that atmospheric transmission is the 

 common channel of infection in yellow fever. As everyone knows, 

 it is a disease which, when once installed on board ship, seems to 

 cling to it tenaciously, more particularly in the hold, magazines, 

 merchandise, and in all close and restricted quarters. Humidity, 

 heat, and want of light and ventilation have been, until recently, the 

 supposed conditions necessary to the conveyance or harbouring of 

 yellow fever. Sanarelli has further suggested that moulds must be 

 considered "the natural protectors of the specific agent of yellow 

 fever."f By a series of interesting experiments, he demonstrated 

 the stimulating effect which moulds have upon gelatine-plate cultures 

 of this bacillus in the laboratory. Outside the laboratory, in houses 

 and on ships, the conditions favouring the growth of moulds appeared 

 also to be the conditions favouring yellow fever. For instance, 

 humidity, heat, and scanty aeration are highly favourable to mould 

 growth, and thus, according to Sanarelli, to yellow fever. To these 

 factors, also, is supposed to be due the unhealthiness of Eio Janeiro. 

 During the yellow fever epidemic in Montevideo in 1872, the 



* Brit. Med. Jour., 1897, vol. ii., p. 7 (Prof. G. Sanarelli), 1900, vol. i., p. 334, 

 and Tlie Medical News (New York), 9th December 1899. 

 t Brit. Med. Jour., 1897, vol. li., p. 11. 



2 C 



