The Trials of Milking Machines , 1913. 
251 
the same variations of temperature, the results are strictly 
comparable. 
Small quantities of milk were taken from these flasks at 
intervals, 10 c.c’s of which were titrated with as little delay as 
possible. 
Owing to the variations of temperature above mentioned, 
it is not possible, with any degree of certainty, to attribute a 
rise in the rate of development of acidity to a progressive con- 
tamination of the tubes and milking vessels with milk 
souring organisms. 
From the morning of Saturday, April 19, to the evening of 
Wednesday, 23rd, a complete series of determinations was 
obtained from the time when some of the samples commenced 
to develop acidity to the time when some began to curdle. The 
average of figures so obtained is given in the following table, 
and indicates considerable differences in the keeping quality of 
milk from the different machines. 
Average of figures obtained by the titration of samples kept for the same time 
at the same temperature , each lot being titrated on at least two occasions. 
Results expressed in gain of lactic acid over original fresh milk per 100 
volumes. 
Samples taken from Saturday morning to Wednesday evening. 
Machine 
Gain percentage 
lactic acid 
Machine 
Gain percentage 
lactic acid ■ 
D. 
0-07 
Q. 
0-23 
0 . 
0-09 
A. 
0-25 
E. 
0-13 
H. 
0-26 
N. 1 
0-18 
P. 
0-28 
F. 
0-21 
K. 
0-29 
Gr. 
0-22 
i Average for four days only. 
The above order was in general maintained when the whole 
period of the trial was taken into account. 
It must be pointed out that all these results are good, more 
than half of the samples developing not more than 0T per cent, 
lactic acid in three days in spite of the warm room in which 
they were kept. 
The curdling of the milk did not coincide with the develop- 
ment of any particular amount of acidity as measured by the 
titration, some milks developing more than twice as much 
acidity as others before they curdled. This is not to be won- 
dered at, considering the varied bacterial flora, nor can any 
close agreement be looked for between the bacteriological 
counts and the observed development of acidity. The figures 
given do, however, indicate the keeping qualities of the milks, 
which are good. 
