12 BULLETIN 940, U. S. DEPARTMENT OF AGRICULTURE. 
of this test from the highest grade of milk that could be produced. 
The results with the 10 c c, amount of milk were not found to be so 
satisfactory as the 20 c. c, because during the examination of cer- 
tified milk a positive test was rarely encountered with the smaller 
amount. 
It was felt that an amount of milk should be used which if pos- 
sible would show at least one positive reaction in a set of 10 tubes 
with milk produced under the cleanest conditions, and would show 
also a large number of positive reactions with milk produced under 
extremely dirty conditions. The results in Table 3 show that 2 c. c. 
amounts of milk do not meet this requirement, for with dirty milk 
8 out of 30 samples gave no positive sporogenes test. In the same 
dirty milk there was a greater tendency for a larger number of 
the 10 tubes with 20 c. c. each to show the characteristic stormy reac- 
tion. Even with the 20 c. c. quantities the results were not so uni- 
formly high as could be desired, but this amount of milk possessed 
the added advantage of being about the smallest amount which could 
be used to show positive reactions in milk produced under the cleanest 
conditions. 
THE SPOROGENES TEST IN RELATION TO MILK PRODUCED UNDER 
EXTREME CONDITIONS OF CLEANLINESS AND OF FILTH. 
It was evident that if the sporogenes test could not differentiate 
between samples of milk produced under clean and dirty conditions 
there could be no hope of the test's being of value in milk-control 
work. To determine this point the sporogenes test, using 10 tubes 
with 20 c. c. of milk, was applied to 24 samples of certified milk and 
18 samples of milk produced under the dirty conditions previously 
described. The results in Table 4 show that the test with 20 c. c. of 
milk to each tube can be used with milk produced under extremes 
in conditions. About 50 per cent of the samples of certified milk 
showed no positive reaction, but of the remaining 13 samples 7 
showed 1 positive tube, 5 showed 2 positive, and 1 showed 4 positive. 
