CHICKEN CHOLERA 279 



die quickly, while the guinea-pig which furnished the 

 virus, recovers without the least suffering. We are 

 present here, then, at a restricted evolution of a micro- 

 scopic organism which causes the formation of pus and 

 a closed abscess without bringing about any internal 

 disturbance or the death of the animal on which it 

 occurs, and, nevertheless, one which is always ready to 

 convey death to other species into which it is inoculated, 

 ready even to kill the animal on which it occurs in the 

 form of an abscess, if more or less fortuitous circum- 

 stances enable it to pass into the blood or into the 

 splanchnic organs. 



''Chickens or rabbits which live in the company of 

 guinea-pigs bearing such abscesses may suddenly become 

 sick and die without the health of the guinea-pigs appear- 

 ing to be in the least impaired. For this to occur, it 

 is only necessary that the abscesses of the guinea-pigs 

 should rupture, scattering a little of their contents on 

 the food of the chickens and the rabbits. An observ- 

 ing person, seeing these facts and ignorant of the rela- 

 tion of which I am speaking, would be astonished to see 

 chickens and rabbits destroyed without any apparent 

 cause, and would believe that the disease was sponta- 

 neous, for he would be far from supposing that it had 

 originated in the guinea-pigs, all in good health, especially 

 if he knew that the latter are also subject to the same 

 disease. How many mysteries in the history of conta- 

 gions will some day receive solutions still more simple 

 than that of which I have just been speaking! Let 

 us reject theories which we can contradict by convincing 

 facts, but not on the vain pretext that certain of 

 their applications escape us. The combinations of 

 nature are at the same time more simple and more 

 varied than those of our imagination!" 



For anyone who pondered over Jenner's work, what was 



