196 
Journal of Agricultural Research 
Vol. II, No. 3 
flasks subjected to analysis were examined to ascertain their freedom 
from growth of other organisms. 
It has been observed that active lactic acid is the main form of this acid 
in fresh cheese curd, but that it rapidly changes to the racemic variety. 
In addition to the foregoing studies on substances formed by bacteria, this 
paper also includes some work done on the agencies which cause these 
changes in the form of lactic acid present in cheese and which take place 
during the earlier period of cheese ripening. 
In the preceding article (Evans, Hastings, and Hart) the presence of 
coccus forms in normal Cheddar cheese is demonstrated. It is shown 
that nonliquefying cocci which ferment lactose in milk cultures are 
always present, in percentage of the total bacterial content ranging 
upward to 50. The cocci are distinguished from the Bacterium lactis 
acidi group by their morphology and by the extent of reduction of litmus 
in milk cultures. In cultures of the B. lactis acidi group the cells are 
in pairs, and some or all of the cells are elongated; there is always a 
characteristic reduction of litmus. The cocci include those cultures in 
which the cells are spherical. The complete reduction of litmus beneath 
the surface layer, characteristic of the B. lactis acidi group, does not 
take place. 
A classification of the cocci occurring in this type of cheese is made. 
They are divided into two groups on the basis of morphology: Streptococci 
and micrococci. Those occurring in pairs are included with the strep¬ 
tococci, together with those which form chains of varying lengths. The 
microccocci are the Coccacese which divide in two planes; consequently the 
cells appear in pairs, fours, or bunches. Most of the cultures of this group 
produce a heavy growth upon agar slant, which is often of some shade of 
yellow. A further differentiation of the groups into varieties is made on 
the basis of fermentation of the following test substances: Lactose, 
salicin, sucrose, glycerin, and mannit. This classification of the cocci is 
given in Table I. The substances produced by representatives of several 
of these varieties have been analyzed, and the data are presented in 
Tables II to X. 
Table I .—Differentiation of the coccus groups into varieties 
