EFFECT OF TEMPERATURE ON BACTERIA. a3 
disappeared as time elapsed. ‘This shows, of course, that these 
types of bacteria can be of little or no significance in the phe- 
nomena that occur, and can have had practically no influence 
upon the milk. 
The species of bacteria which continued to develop during 
the whole of the experiment were Groups I., III., [V., VI., and 
VII., all of which we found in earlier experiments. The neutral 
bacteria, Group IV., developed abundantly; the acid Groups I. 
and III. and the liquefying bacteria, Groups VI. and VII., all 
developed extensively. 
In the last experiments also there was a large number of 
bacteria whose species could not be determined. There is no 
question that these practically all belonged toGroups I. and IV., 
but at the time when the plates were counted it was impossible 
to differentiate them definitely because of the large numbers of 
liquefiers present. 
Perhaps the most striking feature of this experiment was the 
development of the liquefying bacteria, which, during the entire 
series of tests, not only constantly increased in numbers, but 
remained in a constantly high percentage, and, even at the end, 
comprised 13 per cent. of all the bacteria present. Recognizing 
that the liquefying bacteria are likely to produce putrefactive 
products, it is, of course, significant to find that these bacteria 
remained so numerous in this sample of milk, which had been 
preserved at the temperature of 10”. 
Milk kept at 20°.—It will be seen that this experiment differs 
somewhat from those described above, in that the milk which 
was kept at 20° did not show the usual development of the 
ordinary lactic bacteria, Group I. At the time of curdling, this 
group of bacteria comprised only about 21 per cent. of the whole, 
while Group III. comprised 37 per cent. of the whole. In this 
respect, then, the result was somewhat unique, and suggested 
that there are some conditions other than those of simple tem- 
perature which determine whether or not the bacteria of the 
first group shall get the upper hand of the other species. 
It will also be noticed that practically all of the species found 
in the first sample of milk continued to develop during the entire 
period, and were present in about equal quantities at the end. 
ye 
