540 EXPERIMENTAL RESEARCHES WITH CHICKEN-CHOLERA MICROBES, 



(c) The foregoing experiment being unsatisfactory in its results, on account 

 of the high mortality among the rabbits from causes other than 

 "chicken-cholera," the Commission decided for another large experi- 

 ment. 



For this purpose, the main enclosure on the Island (see above) was 

 divided into two nearly equal portions by means of a double fence of 

 rabbit-netting, with a clear space of one yard (about 92 cm.) between. 

 The one division, which may be called the disease-division, contained 

 about 136 running feet of artificial burrow ; these burrows were old ones, 

 formerly used, but here and there altered. In the other division, 

 henceforth called the control-division, there was a total of about 95 

 feet of artificial burrow ; there were two of such burrows, one old one, 

 somewhat changed, and another fresh made. 



The arrangement was, to turn into each of these divisions ^y^i!?/ healthy 

 rabbits, not fed on the chicken-cholera microbes ; to add to the fifty in 

 the disease-division three batches of five rabbits for each, which had 

 been fed on fresh cabbage -leaves sprinkled with 2 ccm. of a virulent 

 broth-culture of the microbe of chicken-cholera for each rabbit. The 

 first batch was to be turned in at once, the second after a week, and 

 the third after a fortnight ; the experiment was to be completed after 

 three weeks from the outset. 



The experiment was begun on February 12th, 1889, and concluded 

 March 5th, according to programme. 



Although the whole enclosure had been used from November 7th to 

 the 29th, 1 888, for the carrying out of the experiment mentioned under 

 (b), p. 538, 1 did not think it necessary to specially disinfect it, in view 

 of the new experiment. From the end of November, after the former 

 experiment, some twenty rabbits were left there till the 24th January, 

 without anyone dying from " chicken- cholera." During the interval, 

 sunshine and wind could act on, and must have proved disastrous to, 

 any chicken-cholera microbes that might have been deposited there. 

 Then again, one portion of the enclosure was, in the fresh experiment, 

 reserved as control-division, stocked with a considerable number of 

 rabbits ; of these, I may just as well state beforehand, not a single one 

 perished from " chicken-cholera." 



The result of the experiment which was carried out as said above,* 

 was as follows : — 



* Throughout this experiment I employed broth-cultures which had been obtained 

 directlj from fresh heart-blood of rabbits, inoculated for that purpose with "chicken- 

 cholera." The tubes containing- the microbe-infected broth were placed in a thermostat 

 kept at about 38° C, where they remained for about 24 hours before being used. A tem- 

 perature of that degree appears to answer for the growth of the microbes better than any 

 other. 



