EXPERIMENT STATION BULLETINS. 413 



quency and its high number, which goes up to several millions in some samples. 

 It behaves about the same as Bad. I. Connii. It is comparatively seldom 

 found in the fresh butter (perhaps its colonies on the agar plate could not be 

 distinguished easily from the more frequent lactic colonies), it develops in 

 the storages rapidly, in spite of the cold and salt, and we find it in 127 out 

 of 168 tubs. The February examination shows a decrease in number, but 

 not in frequency. The liquefying yeast is not so often found in the warm 

 storage, but keeps its frequency in the colder ones. The round yeast, on the 

 contrary, grows almost exclusively on the samples a. The pink yeast dis- 

 appeared in the coldest storages in February. Its number was always so small 

 that we did not pay any attention to it. 



The distribution of Streptothrix is not very regular, probably because it is 

 impossible to make exact counts of these hard, tough organisms, which stick 

 together. This is to a certain extent true also with the molds, but our tables 

 show very plainly the slow decrease of Oidium in comparison with the fresh 

 butter and more distinctly of the Aspergillus and Penicillium. Penicillium, 

 and to a certain degree, Aspergillus, developed to a greater extent in the 

 warm storages. 



COMPARISONS OF OUR MICRO-ORGANISMS WITH THOSE FOUND BY OTHER 



AUTHORS. 



Comparing the micro-organisms which we found with those isolated by 

 other investigators from fresh and old butter the results disagree very de- 

 cidedly. Almost all other investigators found several species of micro- 

 organisms regularly present in butter, whereas we have besides the lactics 

 the only one, small, irregular yeast, which was almost always present; the 

 Micrococcus lactis varians was only in half of our samples and the rest oc- 

 curred even less frequently. This difference is mostly due to the different 

 temperature. The temperature below the freezing point makes the con- 

 ditions for development very unfavorable, whereas the room temperature 

 which the other investigators used for keeping their samples gives very good 

 conditions for the multiplication of germs. The higher average salt content 

 of American butter, compared with that of European origin, helps also to 

 decrease the number and the kinds of organisms. Besides that, the butter 

 of those investigators became rancid within a few weeks, whereas, on ac- 

 count of the entirely different conditions, we did not begin our first ex- 

 amination until after the tubs had been in storage for at least five months. 

 It must be considered also, that we had a greater variety of very different 

 samples than most of the other authors, and therefore there was a greater 

 probability that some of them would lack species which were found fre- 

 quently in many other samples. Since the conditions for the fresh butter 

 were quite different, we cannot be surprised to fuid the difference still more 

 pronounced in the old butter, for the chemical changes were different, the 

 acidity not increased and the butter altered in some other way. 



Let us compare now our bacteria with those found by other investigators 

 in ordinary fresh and rancid butter. 



Krueger found in a sample of cheesy butter Micrococcus acidi lactis. Ba- 

 cillus fluorescens non-liquefaciens, 2 species of Saccharomyces, Oidium lactis. 

 Lactic acid bacteria. 



These organisms, except the two kinds of Saccharomyces, were found also 

 in some of our samples, M. acidi lactis probably being identical with 

 M. lactis albidus. 



