BY DR. OSCAR KATZ. 549 



attaining a greater poisoning strength in its action on rabbits, 

 by means of such successive transmissions, the consequence will 

 naturally be that, under the same conditions, the period of incuba- 

 tion and actual disease, or the whole period from infection to death, 

 becomes shorter, until a certain stationary point is reached ; this 

 period must, on the other hand, provided the conditions be the 

 same, become longer, or infection with subsequent death may not 

 follow at all, if there should be any decrease or attenuation of the 

 virulence of the microbe. Should the latter preserve its degree of 

 virulence uniformly from the first rabbit to the last, it stands to 

 reason that the above period will remain about the same through- 

 out, provided again the conditions be the same. 



The experiment was carried out in the following manner : — A 

 healthy pigeon was inoculated, October 3rd, with a small quantity 

 of the surface-growth of a virulent stick-culture of the microbe of 

 chicken-cholera (fourth generation, 32 days old). Not long after 

 the death of this pigeon, which died of typical chicken-cholera 

 within about twenty hours, two rabbits were inoculated, each 

 with five platinum-loops full, equal to -j^ ccm., of heart-blood from 

 this pigeon. The blood of the first rabbit that died, or that was 

 found dead, furnished the material for inoculation, in like manner, 

 into two further rabbits ; with the blood again of the first of 

 these dead, two other rabbits were inoculated, and so on till the 

 number of forty rabbits, or twenty generations, were arrived at, 

 when the experiment was concluded. 



Before directing attention to the table of results of the experi- 

 ments given below (Table III., at the end), I wish to state the 

 following: — The rabbits used were, if not specially noted to the 

 contrary, full-grown animals of normal appearance. If at the 

 2?ost-7nortem examinations anything abnormal was found, it will 

 be remarked in that table. The rabbits for this experiment were 

 taken irrespectively of the sex. From practical reasons it was not 

 possible to employ either males or females from the beginning to 

 the end. 



