200 THE CONTAGIOUS TYPHUS 



tion of the poison, in order to guard and de- 

 fend life against the danger which threatens it. 



4th. A malady essentially general, tol'm* 

 substantive, it directs its action, in different 

 degrees, over the whole structure, but chiefly 

 on the nervous centres, on the organs of re- 

 spiration, and on the digestive apparatus. 



5th. Its progress is regular; to the latest 

 period of incubation it succeeds that of the 

 general poisoning of the blood that of the 

 pyrexia of general fever which for a time 

 stops up all the secretions. Then, the morbid 

 flux is localized according to particular predis- 

 positions : either on the nervous centres, when 

 the animal is struck down at the outbreak ; 

 or on the lungs, when the respiratory derange- 

 ments become the leading symptoms ; or on 

 the digestive channels, when the train of ty- 

 phoid phenomena is observable. 



6th. The period of acute inflammation, 

 which had dried up the sources of secretion, 

 gives place to that of the depurative and 

 critical exhalations or secretions ; from every 

 mucous membrane, from every outlet, there 

 issues a mucous discharge, which at first is thin 



