552 EXPERIMENTAL RESEARCHES WITH CHICKEN-CHOLERA MICROBES, 



occurrence there, some such time after death as noted above, can 

 only be declared by their having multiplied there after the death 

 of their hosts. 



The table, the arrangement of which will, I think, be easily 

 understood, contains the results of this experiment. I may at 

 once remark that, for the sake of convenience, those rabbits which 

 as having died first were used for the successive inoculations of 

 the different series (column one), are designated uniformly by the 

 first (odd) number (column two) of each series. (See Table III., 

 at the end.) 



In looking over the figures in this table, we cannot help arriving 

 at the conclusion that by transmitting the virus of chicken-cholera 

 from rabbit to rabbit, to the extent of twenty generations, neither 

 an increase, nor a decrease in its virulence is attained — that, rather, 

 its virulence does not exhibit any striking differences throughout 

 the whole series. It is true that in four cases out of the forty, the 

 figures regarding time of death are a little lower than usual (Nos. 

 1, 21, 29, 33), that in three other cases they are somewhat higher 

 (Nos. 4, 14, 28), and that in one case (No. 34) the figure is very 

 high. But these exceptions may be declared from certain indi- 

 vidual properties of the rabbits employed. It was, as a matter of 

 fact, not possible to take exclusively only such rabbits as were 

 like one another in every respect (age, size, weight, sex, and health). 



That the rabbit No. 34, Series xvii. — a light-grey female, with 

 a white streak running longitudinally from the back of the 

 head over the middle of the head down to the underside of the 

 neck (mammary glands fully developed, containing milk) — did 

 not succumb until two days after inoculation, which had been 

 performed in the usual manner, is very remarkable. Seeing it out- 

 live the first day, I thought of having hit upon another example 

 of immunity in rabbits. The post-mortem examination later 

 on left no doubt as to its having died of "chicken-cholera.'' 

 I may, however, mention that the seat of inoculation differed 

 from that in all rabbits inoculated, in so far as there 

 was a yellowish-white membraneous formation adhering to 



