256 
Journal of Agricultural Research 
Vol. XIV, No. 6 
The use of a relatively large number of controls in the calf inoculation 
tests was due to the fact that these experiments were made at times 
when calves were to be infected for use in the preparation of the regular 
blackleg vaccine for distribution by the Bureau of Animal Industry. 
At such times four to six calves are usually infected; therefore in order to 
add to the value of the test four such animals as controls were employed. 
Tabi^E III .—Results of subcutaneous vaccination of calves followed after months with 
intramuscular injections of blackleg virus 
Calf No. 
Amount 
of vaccine. 
Amount , 
of virus. a 
Result. 
Cc. 
Cc. 
I. 
K . 
10 
Remained alive. 
2 . 
5. 
IO 
Do. 
3 . 
Control. 
10 
Died of blackleg. 
4 . 
...do,.. . 
IO 
Do. 
5 . 
...do.... 
10 
Do. 
6 . 1 
j 
. ..do. .. . 
10 
Do. 
a Virus employed of same character as described in Table II. 
PREPARATION OF THE TOXIC CULTURE FILTRATE 
Eeclainche and Vallee 1 and others have demonstrated that the bacillus 
of symptomatic anthrax when grown under favorable conditions produces 
a true toxin. It has also been demonstrated that animals susceptible to 
blackleg could be effectively immunized against the disease by injecting 
them with small amounts of such toxin-containing filtrates. Consider¬ 
able attention has been paid to this method in Japan by Nita, 2 and in 
this country Eichhorn 3 has recently called attention to it. 
It was at first thought that this toxin was of a very stable nature and 
not materially affected by such influences as air, light, moderate degrees 
of heat, drying, etc. Subsequent investigations, however, have shown 
that such is not the case, but, on the contrary, under various conditions, 
it is more or less unstable. Therefore, in the production of this toxin 
this fact must be borne in mind, and precautions taken throughout the 
process to guard against influences likely to affect the material. 
Numerous types of media have been prepared and tested for the pro¬ 
duction of this toxin, and considerable difference has been found in the 
potency obtained with the various kinds of media. A description will 
be given only of the type of medium the writer considers most 
efficient for toxin production, but the following are other medias 
tried: Dextrose-veal bouillon plus cubes of beef, dextrose-veal bouillon 
1 Eeclainche, E., and Vall£e, H. recherches experimentals sur le charbon symftomatique. 
In Ann. Inst, Pasteur, annee 14, no. 4, p. 202-223. 1900. 
2 Nita. unpublished results. 
3 Eichhorn, Adolph, studies in blackleg immunization with special reference to blackleg 
filtrate. In Jour. Amer. Vet. Med. Assoc., v. 52 (n. s., v. 5), no. 6, p. 653-669. 1918. Discussion, 
p. 663-669. 
