22 
THOMPSON YATES LABORATORIES REPORT 
These observers advocate a prophylactic made of a solution of the nucleo-proteid obtained 
from microbes grown on solid media, and they say that Haffkine concurred with their view when 
he tried to test the strength of his liquid by the quantity of deposit produced in the cultures. 
This no doubt is so, for inasmuch as the bactericidal property is conferred by substances contained 
in the dead bodies of the microbes, he naturally tests the strength of the prophylactic by the 
amount of deposit. The primary object is to produce a prophylactic substance ; but Haffkine, on 
theoretical grounds, thought the supernatant fluid, by virtue of the toxins, conferred power to 
withstand the toxins formed if the persons did contract plague after being inoculated— that is to 
say, it reduced the case mortality ; for these reasons he preferred to keep the supernatant fluid in 
his prophylactic. 
The foregoing results show experimental confirmation of the theory. I recognise that 
many more observations should be made. I used up all the Rabbits procurable in Bombay at the 
time, and was unable to obtain any more, but I hear that these experiments have subsequently 
been repeated and confirmed by Captain Milne, I.M.S., at the same laboratory. 
