BY DR. OSCAR KATZ. 579 



From the results thus obtained we learn again that desiccation 

 in general is fatal to the microbes of chicken-cholera. The higher 

 the temperature during the process of desiccation, the less time is 

 required to destroy their virulence. 



Desiccation of virulent blood lying on, or impregnating small 

 objects such as the silk-threads usedj caused the virus to die off 

 less quickly than is the case with virulent broth-cultures exposed 

 to desiccation under the same circumstances. The reason for this 

 probably is that the superficial portions of the blood drying up, 

 are able to protect the deeper portions for a longer time than is 

 the case with broth-cultures attached to, or saturating small 

 objects, where, by virtue of the composition of the broth, less 

 protection can be afforded to the deeper portions by the superficial 

 ones. 



The fact that a virulent broth-culture of the microbes of chicken- 

 cholera very soon ceases to be eflScacious when exposed, in a thin 

 layer, to desiccation at summer temperatures such as they exist 

 here, must, in my opinion, to a large extent account for the sur- 

 viving, now and then, of wild rabbits, which during summer 

 nionths were ajiven (in shaded hutches) cabbage- or barley-leaves 

 sprinkled with small portions of such a culture, but which were 

 very slow in beginning to eat the infected food, or in finishing it 

 «p, so that meanwhile the liquid spread on it was enabled to dry up. 



Effect of Putrefaction. 



It is ascertained that the bacteria of chicken-cholera, when kept 

 together with other micro-organisms, as in contaminated cultures, 

 are sometimes able to retain their vitality, and power of infecting, 

 for a considerable time, up to three months.* 



For my own part, I have tested how long chicken-cholera 

 bacteria would remain active in rabbit-blood which, containing 



*Kitt, Wert und Unwert der Schutzimpfungen gegen Tierseuchen 

 Berlin, 1886, p. 55. 



