240 THE CONTAGIOUS TYPHUS 



First Period of Incubation. 



We have said that infectious diseases, when 

 once the frame had suffered the effects of 

 the poisonous miasma, pursued their fatal 

 course, and that, generally speaking, it was 

 impossible after such infection to arrest its de- 

 velopment. We say generally, for the typhus 

 at the outbreak of its appearance on a virgin 

 soil sometimes manifests itself in a benignant 

 manner, then it becomes more destructive, 

 by-and-bye its pernicious properties decline, 

 and it in some sort goes out of itself. One 

 would say that the epizootia, like those it 

 smites, has likewise its peculiarities, its period 

 of initiation, of duration, and of decline. 

 There are in consequence fixed times or epochs 

 during which the sufferers afford better scope 

 for our means of action ; at a given moment 

 the attenuated virus, having lost much of its 

 deadly effects, ceases to produce death, which 

 decline is the real source of the marvellous 

 successes obtained by certain remedies against 

 the epizootia. 



If it be true that the distemper at its period 

 of duration, and at its most critical moment, 



