262 
Journal of Agricultural Research 
Vol. XIV, No. 6 
were found highly efficient in immunizing experiments. In the case of 
the culture filtrate the toxicity of the material was readily demonstrable 
and its potency appears to depend on its being toxic. 
It is possible, therefore, that immunization with blackleg natural 
aggressin is brought about through the production of “antiaggressins,” 
while with the toxic culture filtrate immunity is acquired through the 
production of antitoxin. 
It is highly desirable that an entirely satisfactory and practical method 
of concentration of the toxic culture filtrate be obtained. Some of the 
methods which have been employed in the past are wholly or in part 
unsatisfactory, the toxin being either totally destroyed or its potency 
considerably lowered. As the toxicity of the culture filtrate is appar¬ 
ently related to its potency, obtaining the toxin in a pure or concentrated 
form would permit the production of an accurately standardized product 
of uniform dosage, based on the minimal lethal dose of the toxin for 
guinea pigs of a given weight. 
In the filtration of the toxic culture some of the toxin is lost as a 
result of such process. It is therefore essential that the product be 
subjected only to such filtration as is necessary to insure the removal of 
all organisms. 
It is hardly necessary to emphasize the economic importance of the 
toxic culture filtrate as compared with the natural aggressin, since the cost 
of its production is only a small percentage of that necessary to prepare 
the natural aggressin. 
CONCLUSIONS 
(1) Blackleg natural aggressin and toxic culture filtrate are highly 
valuable agents in immunization against symptomatic anthrax. 
(2) Martin’s peptone solution to which have been added ground beef 
and dextrose is best suited for the preparation of the toxic culture 
filtrate. 
(3) The blackleg toxin is susceptible to such influences as air, light, 
heat, etc., and in order to insure a potent product measures should be 
employed to minimize its exposure to the same. 
(4) There is apparently a direct relation between the toxicity of the 
culture filtrate and its potency. 
(5) Virulent bouillon cultures of the bacillus of symptomatic anthrax 
to which lactose has been added and which are then dried and pulverized 
give very satisfactory results as a test virus in standardization tests of 
blackleg immunizing agents on guinea pigs. 
(6) There is apparently a distinct difference between the immunizing 
principles in blackleg natural aggressin and blackleg toxic culture 
filtrate. 
(7) A uniformly satisfactory and practical method of isolating or 
concentrating the blackleg toxin is highly desirable. 
