
BACTERIA IN THE DAIRY. 63 
bitter, sour butter, while No. 16 made very good butter in all 
cases. So marked was the bitter taste of 162 that it was used in 
many experiments at the Columbian Fair to show the injurious 
effect of certain species of bacteria on the butter aroma. The 
difference between these two organisms is very remarkable con- 
sidering that their specific characters are almost identical. 
After having worked out the characters as shown on page 51, 
I concluded that the species were identical, but repeated experi- 
ments in ripening cream showed an absolutely uniform difference 
in the resulting butter, and the conclusion was inevitable that at 
least there was a physiological difference between them. This 
result, while surprising, is not unique, for other species or varie- 
ties have been found to be separated by equally slight differences. 
Nencke (Cen?’t’t. f. Bact. u., Par. 1X, p. 304) has found a bacillus 
differing from B. coli commune only in producing a different 
chemical form of lactic acid. Other instances might be cited. 
Species No. 8. 
From experiments 68—73 it will be seen that No. 18 produces 
very poor butter. It is not so bad as that of Nos. 27 or 162 but 
is of a decidedly poor quality. 
Species Vo. 19. 
In experiment No. 74 the cream was heated to too” instead of 
70° which explains the scalded milk taste. No. 19 will not grow 
at 35° (see page 52). The ripening of the cream in experiment 
75 was not, therefore, due to No. 19 but to the organisms which 
resisted 70° used in pasteurization and were forced into rapid 
growth by the high temperature of ripening. From experiments 
74-77 it will be seen that No. 19 is not favorable to butter 
ripening, butter acquiring a rather strong taste under its influence. 
The butter was not very bad, however, and would readily pass 
in market as a second quality butter. 
Species LVo. 20. 
The butter in experiments Nos. 78-82 differed somewhat in 
quality, sometimes being quite good and at others not so good. 
The differences were very slight, however, and would lead to the 
conclusion that No. 20 produced very slight effect on butter 
flavor. So slight was it that the organism was soon abandoned 
as unpromising. 
