176 
Journal of Agricultural Research 
Vol. II, No. 3 
There is a great variation in the amount of acidity formed in milk by 
the various cultures of a given strain. In Table V are given the range of 
maximum percentages of acidity found within the strain. The average 
percentage of acidity formed by the cultures increases with the ability 
to break down the more complex test substances. The average per¬ 
centages for the three varieties are given in Table VI. The acid has 
been calculated as lactic acid. 
Table V. —Range of percentages of acidity formed by the strains of Bacterium casei 
Strain No. 
Number of 
cultures 
studied. 
Range of max¬ 
imum percent¬ 
ages of acidity. 
Strain No. 
Number of 
cultures 
studied. 
Range of max¬ 
imum percent¬ 
ages of acidity. 
I. 
I 
0. 68 
7. 
12 
0. 91 to i. 97 
. 94 to I. 69 
I. 38 to 1. 80 
*97 
. 86 to 1. 60 
2. 
60 
. 10 to 1. 52 
• 73 to 2.37 
. 42 to I. 50 
• 47 to 1. 97 
• 85 to 1. 35 
8 . 
6 
2 . 
8 
14 
I 
4 . 
12 
10 . 
c . 
16 
11 . 
6 
6 . 
c 
12 . 
1 
1. 74 
0 
Table VI. —Variation in the average percentage of acidity formed by the varieties of 
Bacterium casei 
a 
b 
c 
Variety No. 
Number of 
cultures 
titrated. 
Average per¬ 
centage of 
acidity. 
60 
o *75 
7 2 
1.03 
10 
1.23 
The statement was made in a previous publication (Hastings, Evans, 
and Hart, 1912) that the width of the cells of the lactic bacilli in a pure 
culture appear to be fairly constant, but that in come cultures the indi¬ 
vidual cells are all slender, whereas in other cultures they are all com¬ 
paratively thick. Measurements have been made of the width of the 
cells in many cultures. The averages for the three varieties are given 
in Table VII. 
Table VII. —Variations in the average width of the cells of the varieties of Bacterium casei 
Variety No. 
Number of 
cultures 
measured. 
Average width 
of the cells in 
microns. 
a. 
2 5 
22 
3 
I. 06 
.81 
• 53 
b. 
C. 
Thus, it is shown that the width of the cells decreases with their ability 
to attack the more difficultly fermentable substances and with their ability 
to produce higher percentages of acidity. The differences in width are 
so great that with a glance at a microscopic field of a culture containing 
