538 EXPERIMENTAL RESEARCHES WITH CHICKEN-CHOLERA MICROBES, 



(b) In this experiment the whole of the large enclosure, already referred 

 to, was utilised. This enclosure, which measured 100 feet by 80 feet, 

 contained artificial burrows, in all about 185 running feet. 



On November 7th, 1888, one hundred rabbits, mostly full-grown and 

 only a few half or not quite full-grown, were let loose in that enclosed 

 place. The rabbits were, as the result later on showed, mostly in a 

 poor condition. Shortly afterwards, ten rabbits which had been fed on 

 cabbage -leaves sprinkled with 2 ccm. of active broth-culture for each 

 rabbit, were placed with the former in the same enclosure. On 

 November 14th, another batch of similarly infected rabbits, this time 

 six, among which three Tasmanian ones, were introduced. Lastly, on 

 November 22nd, a third batch of six infected rabbits,* also fed on 

 2 ccm. culture,t were let loose in the same enclosure. On November 

 29th the period of observation terminated. 



Infected Babbits. — Of the tiventy-tioo infected rabbits thus turned 

 loose among other uninfected ones, ticenty-one succumbed, while the 

 twenty-second survived. (It died, however, December 3rd, P.M. 

 negative.) Of the twenty-one, three were removed from the enclosure 

 shortly after they were found dead, and examined (one, each, of the 

 first, second, and third batch). The result of the examination was in 

 the first ca.se positive (rabbit found dead inside burrowj, in the second 

 and third, nec/ative. The other rabbits, eighteen in number, were not 

 taken out of the enclosure until the conclusion of the experiment, 

 November 29th. Twelve of these eighteen died outside, six inside the 

 burrows, t The proof of those eighteen having died from " chicken- 

 cholera " was furnished partly by control-experiments on other 

 rabbits, partly by the appearance of the carcasses — which showed rigor 

 mortis exceedingly well-marked, in contrast to other rabbits which 

 perished from some indiflferent causes (except, of course, any septi- 

 caemia similar in effect to chicken-cholera) — partly by the charac- 

 teristic symptoms which some of the rabbits under consideration were 

 observed to exhibit when dying, or some time before death. Lastly, 

 the diagnosis was made sure by the positive results of the direct 

 microscopical examination of cover-glass preparations of blood derived§ 



* The consignment of rabbits, of which these six formed part, had been received on the 

 Island only the previous day. 



t The cultures used in this experiment were derived directly from blood of rabbits 

 dead from "chicken-cholera," and incubated at 39-40°C for 24 hours before being used. 



X The burrows, of course, were opened and examined from time to time. 



§ This was done each time by means of a clean sterilised glass-tube, which had been 

 drawn out in the flame into a fine end of some length. By pushing this fine end through 

 a suitable spot at either the right or the left side of the thorax, from which spot the hair 



