456 YELLOW FEVER. 



one of the clinical signs of the disease in its worst form. 

 Anuria, coma, and cardiac collapse usher in a fatal issue. The 

 mortality varies in different epidemics from about 35 to 99 per 

 cent of those attacked. Both white and black races are sus- 

 ceptible, but those who have resided long in a country are less 

 susceptible than new immigrants. An attack of the disease 

 usually confers complete immunity against subsequent infection. 

 Post mortem the stomach is found in a state of acute gastritis, 

 and contains much altered blood derived from haemorrhages 

 which have occurred in the mucous and submucous coats. The 

 intestine may be normal, but is often congested and may be 

 ulcerated ; the mesenteric glands are enlarged. The liver is in 

 a state of fatty degeneration of greater or less degree, but often 

 resembling the condition found in phosphorus poisoning. The 

 kidneys are in a state of intense glomerulo-nephritis, with fatty 

 degeneration of the epithelium. There is congestion of the 

 meninges, especially in the lumbar region, and haemorrhages 

 may occur. The other organs do not show much change, 

 though small haemorrhages under the skin and into all the tissues 



of the body are not infrequent. 

 In the blood a feature is the 



ff, m ^^ * - excess of urea present, amount- 



ing, it may be, to nearly 4 

 / ^, per cent. 



' J& * "J^ The Etiology of Yellow 



"* ^t. 4 " ***& -/ * Fever. Two chief views are 

 ^/; :/ here held, (i) That the dis- 



+ ' ' ease is caused by a bacterium 



~:" ' '-, ' belonging to the B. coli group 



\ t , t ^ and called the B. icteroides. 



(2) That the causal agent is 

 of such small size as to be 



FlG. 155. Bacillus icteroides, from a . ,-, ,-, > 



young culture on agar (Sanarelli). x 1000. microscopically invisible, and 



that for the transmission of the 



disease from man to man a mosquito acting as an intermediate 

 host is necessary. This latter view, which chronologically is 

 second, now holds the more important position. 



i. Bacillus icteroides. A very full research into the bacteriology of yellow 

 fever was that of Sternberg (1890), the result of which was that of various 

 organisms isolated one which he named " bacillus x " appeared possibly to 



