
ASEPTIC MILK. 59 
averaged 23 per cent., in the aseptic milk they averaged 42 per 
cent. This suggests, of course, that certain species of lactic 
bacteria are found in the milk ducts, and hence are not removed 
by our aseptic precautions. It is to be emphasized, however, 
that in none of these cases were the acid bacteria found the 
typical Bact. lactis acidi, but were always other species of less 
common and less well known dairy organisms. 
COMPARISON OF ORDINARY MILK AND ASEPTIC MILK KEPT 
ATO | 
1. The first point noticed is the very slight growth that 
takes place in the course of 12 hours in all samples. In the 
aseptic samples there was an average increase of three-fold; in 
the non-aseptic samples an average increase of ten-fold. This 
difference between the rapidity of increase in the ordinary and 
in the aseptic milk was found not only in the average, but alsoin | 
practically every sample. In other words, in every test the 
bacteria multzplied more rapidly in the ordinary milk than in 
the aseptic milk. The interpretation of this fact is not clear, 
although a simple suggestion would seem to explain it without 
much difficulty. The aseptic milk contains mostly bacteria 
that were in the milk ducts, where they are of course accus-, 
tomed to a warm temperature and, therefore, to conditions very 
different from those of the milk after itisdrawn. Consequently 
the bacteria in milk containing only the bacteria from the udder 
contains a larger proportion of individuals unable to develop at 
a temperature of 70°. ‘The non-aseptic milk, however, being 
contaminated largely with bacteria from external sources, con- 
tained more individuals capable of growing at a lower tempera- 
ture, and therefore at the end of 12 hours showed a greater rate 
of increase. 
2, The reduction of the number of bacteria from a few 
thousand in ordinary milk to a few hundred in aseptic milk 
has a very decided effect upon the number which may be ex- 
pected at later periods of 12, 24, and 36 hours. The non-aseptic 
sample, which had at the outset an average of 3,888, showed at 
12 hours 33,000, at 24 hours about 29,000,000, and at 36 hours 
356,000,000. ‘The aseptic sample, having an average in fresh 
milk of 267, showed at 12 hours 663, at 24 hours 1,176,000, and 
at 36 hours 55,000,000. ‘This difference is more striking if the 
