I. EXPERIMENTS ON THE IMMUNIZATION OF GUINEA PIGS BY 
THE INOCULATION OF AVIRULENT TUBERCLE BACILLI IN 
AGAR. IU. OBSERVATIONS ON ANIMALS INOCULATED 
WITH TUBERCULOSIS FROM LEPERS * 
By MARSHALL A. BARBER 
(From the Biological Laboratory, Bureau of Science, Manila, P. I.) 
In previous experiments” I succeeded in immunizing guinea 
pigs against virulent plague by the inoculation of small doses 
of living avirulent plague bacilli mixed with agar. These ex- 
periments have shown that the agar masses may persist for 
some time (twenty-nine days in one case), and that the plague | 
bacilli multiply freely in such masses injected subcutaneously. 
In the following experiments living avirulent bacilli of tuber- 
culosis were mixed with glycerin agar and inoculated. It was 
hoped by this method to obtain in tuberculosis a more effective 
immunization through the relatively slow absorption of a dose, 
comparatively small at the beginning and gradually increasing 
during absorption. 
The avirulent strain of tuberculosis used was a human strain 
(“ki”), kindly furnished me by Dr. E. R. Baldwin of Saranac 
Laboratory, Saranac Lake, N. Y. It has been long cultivated 
in the laboratory, grows rapidly on glycerin agar, and is of 
very low virulence. In addition, a few inoculations were made 
with an avian strain. 
Series 1, Table I.—In this short preliminary series (series 
I) the interval of time—one hundred sixty-eight days—between 
the immunizing and the virulent, or test, doses was relatively 
long. Only one immunizing dose was given, and that was rela- 
tively small. Some of the animals received avirulent human 
bacilli, mixed with agar, some received avian bacilli, and one 
animal received an emulsion of the avian strain without agar. 
The avian dose was prepared by mixing about 30 cubic centi- 
meters of 5 per cent glycerin agar with 3 cubic centimeters 
of a thick emulsion in salt solution of bacilli from glycerin 
agar culture. The dose of human bacilli was made in the same 
* Received for publication November 24, 1914. 
* This Journal, Sec. B (1912), 7, 245. 
145 
