984 
ANDREW HYDE- 
in, others do not; some grow best in an acid medium, others in 
an alkaline or neutral one. 
Bacteria are destroyed by sunlight, dry air, lack of organic 
matter, antiseptics, and finally certain species are antagonistic 
to others, such as the variety used as a butter starter. About 
200 species are known to be partial to milk and its products. 
The number of bacteria in milk as usually delivered in cities 
is very large. One bacteriologist (de Schweinitz) found an 
average of. 61,886 per cc. in 32 samples. The same observer 
found the average number of bacteria in 132 samples of sani¬ 
tary milk to be 5971 per cc. Another writer states that city 
milk usually contains from 10,000 to hundreds of thousands 
of bacteria to a single cc. Of 32 samples of milk taken from 
milk wagons in the city of Washington, D. C., and exam¬ 
ined by de Schweinitz, one showed only about 2500 per cc. ; 
one 4000 per cc., five others between 10,000 and 15,000 ; six 
between 30,000 and 50,000 and the remainder, 18, over 50,000 
per cc.; in several instances over 115,000 per cc. While he 
found that the majority of 135 samples of sanitary milk varied 
from 200 to 5000 colonies per cc. He inferred that in those 
cases where the number of bacteria was small, the milk was 
collected with considerable care, and the other cases spoke for 
themselves. One observer found that milk drawn in a pasture 
under favorable conditions, contained 88 bacteria per cc., while 
the average from samples drawn in a dark filthy stable was 
685,000 per cc. Sixteen samples of milk collected from groceries 
in Boston contained 4,577,000 per cc. 
The city of Buffalo fixes the maximum limit of bacteria in 
milk for human use at 10,000 per cc. Dirt or filth of any kind 
in milk is a sure indication of bacterial infection. 
If milk is naturally a clean fluid and bacteria constitute the 
chief impurity, the question of their origin, development, etc., 
in relation to milk, is important. Where media suitable for 
their nourishment and growth is plentiful, there they are found 
in greatest numbers. 
( To be continued .) 
