266 BACTERIA IN INFECTIOUS DISEASES. 



prey. An individual difference in susceptibility to 

 the poison, and the survival of the fittest, would 

 in time be very sure to produce a race immunity. 

 This view is not, however, sustained by the ex- 

 periments of Prof. Feser upon rats. In these 

 experiments it was found that rats fed on flesh 

 do not contract anthrax, but that the same rats 

 when restricted to a vegetable diet fall victims 

 to the disease after inoculation with anthrax 

 fluids. 



The immunity of fowls has been proved by 

 Pasteur to be a question of temperature. Accord- 

 ing to Chauveau, multiplication of the bacillus in 

 culture-fluids ceases at 43. This is but little above 

 the normal temperature of the fowl. If, however, 

 the temperature is reduced two or three degrees 

 by immersing the lower part of its body in cold 

 water, the fowl becomes susceptible and dies as 

 the result of inoculation with a fluid containing 

 the bacillus. 



The anthrax bacillus is said to have been ob- 

 served by Pollender in the blood of cattle as early 

 as 1849, and by Davaine in 1850. But the etio- 

 logical importance of the parasite was first recog- 

 nized by the last named observer, and was affirmed 

 in a series of communications to the French 

 Academy, made in 1863 and 1864. The experi- 

 ments of Davaine established the fact of the 

 presence of rod-shaped bacteria in the blood of 

 animals attacked with charbon, and that a healthy 

 animal into which a small quantity of this blood is 



