96 STORRS AGRICULTURAL EXPERIMENT STATION, 
the difference of methods of analysis. ‘The methods used by 
Harrison and Cumming are not described in detail, but appear 
to consist in the use of ordinary gelatin in which the milk is 
inoculated, and then in the isolation from the gelatin of certain 
typical colonies and their subsequent testing by bacteriological 
methods. Such a method is quite inadequate for a qualitative 
analysis of the species of bacteria found in milk. The methods 
which are in use in our laboratory, and which are described in 
another place in this same report, enable us to determine with 
accuracy a// the lactic organisms; but no gelatin plates which 
fail to contain litmus or some other similar material can be 
trusted to detect all the lactic organisms and distinguish them 
from others. The colonies produced by many lactic bacteria 
and those produced by the neutral forms above mentioned (our 
Nos. 194, 205, 90, and 224), are almost identical upon common 
gelatin. If the only method of detecting the organisms is by 
studying the common gelatin plates and picking out a few 
samples of colonies to be tested, the neutral forms which fail to 
produce acid would be, in nine cases out of ten, confused with 
the typical lactic bacteria. We are inclined to believe, there- 
fore, that the discrepancy between the results of Harrison and 
Cumming and ours is due to the failure on their part.to use a 
culture medium which will enable them sharply to differentiate 
lactic bacteria from others producing similar colonies in ordi- 
nary gelatin. Whether this be true or not, it is certain that 
in this locality, and if we may trust the work of Freudenreich 
and Barthel, in Europe also, milk as drawn freshly from the 
cow does not contain the Bact. lactis acidi, or contains it only 
in small numbers and shows usually only a comparatively small 
percentage of lactic bacteria. 
GENERAL SUMMARY. 
The most important conclusions which have been reached by 
the papers described in this report are the following: 
1. For further advance in dairy bacteriology qualitative 
analysis of species must be substituted for quantitative analy- 
sis, the former promising to show a totally new series of facts 
concerning the problems of milk bacteria. 
