Aug. 5.1918 Immunization Methods against Symptomatic Anthrax 255 
POTENCY TESTS OF THE GERM-FREE VACCINE OR NATURAE 
AGGRESSIN 
A number of tests have been carried out on calves and guinea pigs to 
determine the potency of this biological product and the results obtained 
have been very satisfactory. The samples tested were from various 
sources, the greater part of them being submitted by commercial houses 
in connection with applications for licenses to market the product 
interstate. 
The early tests of this product on guinea pigs were not nearly so satis¬ 
factory as the tests on calves, owing in a large measure to the character 
of the virus employed for the subsequent infection of the vaccinated 
guinea pigs. This test, however, has been much improved through the 
use of a different type of virus which is described on page 260. 
The results of all the tests carried out with this product will not be 
tabulated, but the following three tests are given as examples of the 
results uniformly obtained (Tables I—III). 
Table I. —Results of subcutaneous inoculation of guinea pigs with germ-free vaccine 
followed after 14 days by intramuscular inoculation with blackleg virus 
Guinea- 
pig No. 
Amount 
of vaccine. 
Amount 
of virus.a 
Result. 
I . 
Cc. 
I . 
Cc. 
0. 5 
Dead of blackleg in 24 hours. 
2. 
I. 
• 5 
Marked swelling but remained alive. 
3 . 
2. 
• 5 
Dead of blackleg in 30 hours. 
4 . 
2. 
• 5 
Dead of blackleg in 48 hours. 
5 . 
3 . 
•5 
Slight swelling, remained alive. 
6. 
3 . 
• 5 
Do. 
7 . 
4 . 
• 5 
Dead of blackleg in 36 hours. 
8. 
4 - .. 
. 5 
Remained alive. 
9 . 
. Control. 
• 5 
Dead of blackleg in 24 hours. 
10. 
...do_ 
• 5 
Dead of blackleg in 32 hours. 
a The virus employed in this instance was prepared by emulsifying 10 gm. of ground affected muscle 
tissue from a calf dead of blackleg with 30 cc. of physiological salt solution, and filtering through a thin 
film of cotton. 
Table II .—Results of subcutaneous vaccination of calves followed after 14 days with 
intramuscular inoculation of blackleg virus 
Calf No. 
Amount 
of vaccine. 
Amount 
of virus. a 
Result. 
I . 
Cc. 
Cc. 
IO 
10 
IO 
IO 
IO 
IO 
Remained alive. 
Do. 
Died of blackleg. 9 
Do. 
Do. 
Do. 
2 . 
5. 
Control. 
... do.... 
A . 
*T * * * * " 
c . 
.. .do.... 
6 . 
...do_ 
a The virus consisted of a heavy suspension of emulsified affected muscle tissue. 
