PROTECTIVE INOCULATIONS. 279 



notably Koch, were not disposed to admit the practical value of Pas- 

 teur's anthrax inoculations. At the conclusion of an elaborate me- 

 moir published in the second volume of the " Mittheilungen " of the 

 Imperial Board of Health of Germany (1884), Koch and his collab- 

 orators (Gaff k v and Loffler) say : 



"As now a certain immunity against inoculated anthrax cannot be ob- 

 tained by the method of Pasteur, as we have seen, without considerable 

 losses, and as the immunity secured at the expense of considerable loss is 

 only an imperfect protection against contracting anthrax in the ordinary 

 way, we must consider the protective inoculations heretofore practised as of 

 doubtful utility, especially when we remember that the second inoculation 

 with a yet stronger virus causes the death of more animals which may serve 

 to further spread the disease." 



The attenuating influence of light on the anthrax bacillus and the 

 fact that cultures attenuated in this way may be used for protective 

 inoculations was first ascertained by Arloing (1886). Eoux subse- 

 quently (1887) showed that the presence of oxygen is a necessary fac- 

 tor in the sterilization of cultures by exposure to sunlight. Behring, 

 wJio has since been so active in the field of research to which the 

 present volume relates, published an article in the Centralbkitt fiir 

 klinische Medicin in 1888 (September 22d) in which he attempted to 

 explain the natural immunity of white rats against anthrax infection. 

 His conclusions are given as follows : 



"1. The blood-serum of white rats is not a favorable medium for the 

 anthrax bacillus." 



"2. The blood-serum of rats differs from that of animals susceptible to 

 infection by its gi'eater alkalinity." 



"3. By the addition of an acid to the blood -serum of rats this becomes a 

 favorable medium for the growth of the anthrax bacillus." 



"4. The blood-serum of rats which are treated, during life, in such a way 

 as to reduce the alkalinity of the blood becomes a suitable medium for the 

 development of the anthrax bacillus." 



As we have pointed out in the chapter on Natural Immunity, the 

 true explanation of the facts ascertained in Behring's experiments is 

 probably to be found, not in the germiciclal power of the compar- 

 atively small amount of alkali present in the rat's serum, but in the 

 fact that the germicidal proteid produced by the leucocytes is only 

 soluble in an alkaline medium. In a paper published in the Annals 

 of the Pasteur Institute (August, 1888), Roux and Chamberland have 

 given an account of experiments made by them which establish the 

 fact that immunity against anthrax maj" be established by inoculating 

 susceptible animals with blood from an animal dead from anthrax, in 

 which the anthrax bacilli had been killed by heat or removed by fil- 

 tration (Sur 1'immunite centre le charbon conferee par des substances 



