92 STORRS AGRICULTURAL EXPERIMENT STATION. 
the milk, but simply of the natural dropping out of certain 
species which did not find the milk a suitable medium in which 
to live and multiply. Fresh milk obtained under ordinary 
conditions normally contains a great variety of species of bac- 
teria. -Some species of bacteria which gain access to fresh milk 
do not find it a favorable medium in which to grow, and it has 
been shown by Conn and others that milk when near the sour- 
ing and curdling point normally contains but few species of 
bacteria, often not more than two or three. Somewhere dur- 
ing the intervening time all of the other species disappear. 
This fact suggested that possibly here might lhe the explana- 
tion for the so-called ‘‘ germicidal action.’’ Probably nearly 
all of the species which gain access at the time of milking 
would appear in the plates made from the fresh milk. Certain 
of these species, however, finding milk so entirely different 
from their natural habitat, might soon lose their vitality, and 
not appear in plates made at later periods. ‘These would show 
a smaller number of bacteria.in the milk, not as a result of any 
germicidal property, but simply because some species were un- 
able to live in the conditions afforded by the milk. Among 
the species gaining access to the milk, there might be those 
which could not develop in a medium so different from their 
natural conditions. These might appear in the first plates 
made from fresh milk, but, being unable to multiply, would 
have disappeared before the second set of plates was made. 
Other species, finding the conditions not so distasteful, might 
multiply for a time, gradually losing their vitality and finally 
dropping out. Certain other species’ might find the new con- 
ditions well adapted to their needs, and develop with great 
rapidity from the very start. If such a condition existed, it 
might frequently happen that the dropping out of the species 
which could not grow would be greater than the increase of 
the species which could grow in the milk. ‘This would result 
in the apparent decrease of the numbers of organisms, or the 
so-called ‘‘ germicidal action.’’ In order to prove the truth or 
falsity of the supposition, it would be necessary to make a 
study of the species found in the fresh milk and their behavior 
during the subsequent period through which the so-called ‘‘ger- 
micidal action’’ is supposed to exist. The results of former 
investigations have been based wholly upon numbers, without 
reference to individual species. 
