526 EXPERIMENTAL RESEARCHES WITH CHICKEN-CHOLERA MICROBES, 



In the following I record a number of experiments which were 

 undertaken with a view to ascertaining, whether it was possible 

 to protect rabbits from the effects of virulent chicken-cholera 

 bacteria, by administering to them such liquids in which the viru- 

 lent microbes had propagated, but were afterwards killed by- 

 moderate heat. A preliminary^ experiment had shown me that, 

 by immersing ordinary thin-glassed test-tubes containing fresh 

 broth-cultures of the microbes, in water kept at 60°C. (140°F.), 

 samples of the contents derived after 15, 30, 45, 60 minutes, were 

 proved to be completely sterile in each case. Such sterilised cul- 

 tures I employed of two kinds. The one description of culture- 

 liquid was plain rabbit-broth, of slightly alkaline reaction ; the 

 other rabbit-broth, to which had been added 1 p.c. pe])tone and 

 0-5 p.c. salt ; reaction the same. The cultures to be sterilised were 

 left in the water-bath of the above temperature for 30 minutes. 



I selected ten full-grown, well-conditioned wild rabbits, having 

 been kept on the Island among others, which served me for 

 control-experiments, for about three months. They had so far not 

 been experimented upon, except that they had for some time pre- 

 viously been in an enclosure separated, by means of a double 

 fence of rabbit-netting with fully a yard of space between, 

 from another portion of the same enclosure in which wild rabbits 

 v/ere allowed to die of ^'chicken-cholera," and the dead bodies not 

 removed until some time afterwards. This was, as may be seen 

 later on, for the sake of testing the value of the disease with 

 regard to its possible spread from infected to healthy rabbits under 

 certain conditions. 



The ten rabbits were placed separately in clean, spacious, shel- 

 tered hutches. I first intended to administer the different quanti- 

 ties of sterilised cultures directly per os ; on finding, however, 

 (by trial on an indifferent rabbit) this procedure not safe enough, 

 I gave them to the rabbits in a small portion of bran, of which 

 they were very fond. Bran was also used in these experiments 

 when virulent broth-cultures were fed. To induce the rabbits, the 

 control-rabbits included, to eat the portions given to them at once, 



