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 (Gaffky and Loffler) say: 
‘‘As now acertain 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). Roux subse- 
quently (1887) showed that the presence of oxygen is a necessary fac- 
tor in the sterilization of cultures by exposure to sunlight. Behring, 
who has since been so active in the field of research to which the 
present volume relates, published an article in the Centralblatt fir 
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: 
“4. The blood-serum of white ratsis nota favorable medium for the 
anthrax bacillus.” ; 
“2. The blood-serum of rats differs from that of animals susceptible to 
infection by its greater alkalinity.” 
‘«8. 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 germicidal 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. Ina 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 may 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 ’immunité contre le charbon conférée par des substances 
