eo 
’ MILKING MACHINES es 
the hand and machine drawn milk runs higher than in the 
preceding table, but the relation between, the two is ma- 
terially different. In each case the machine drawn milk con- 
tained many more bacteria than were found in the milk drawn 
by hand. It was evident that the treatment was not keeping 
the machines in a sterile condition. It was found by rinsing 
the inside of the tubes with 50 cubic centimeters of sterile 
water after they were removed from the gold dust solution, 
that large numbers of bacteria were still left in the tubes. In 
some cases several thousand bacteria per cubic centimeter 
were found in this rinse water. | 
THIRD TREATMENT OF THE MACHINES. 
When it was found that the gold dust solution was not 
sufficient to keep the tubes and teat cups sterile, the treatment 
of the machines was again changed. After washing as pre- 
viously described, all the rubber tubes and teat cups were 
placed in a 2% per cent solution of formalin made from the 
commercial 40 per cent formalin. The tubes were allowed 
to lie in this solution between milkings, and were thoroughly 
rinsed with clean water just before use. In Table 28 are given 
the results of a series of tests taken when the machines were 
thus treated. The large tin pail was sterilized by steam, as 
in the case of the previous experiments. It will be noticed 
in Table 28 that in many of the experiments the germ content 
of the machine drawn milk is higher than that drawn by hand 
at the same milking. In some cases this difference is quite 
marked in favor of the hand drawn milk. But in some of 
the experiments, however, the machine drawn milk contained 
fewer organisms than did that drawn by hand. The average 
for all of the experiments is somewhat in favor of the machine 
drawn milk. It was found by testing the tubes with sterile 
water that the formalin solution was making them practically 
sterile, there being but few organisms found in them. It was 
evident from these experiments that the 2% per cent formalin 
solution was sufficient to keep the tubes nearly sterile, and 
it was also found that the solution was beneficial to the texture 
and keeping quality of the rubber. It was, however, some- 
what injurious to the tin covered teat cups, and made them 
corrode somewhat rapidly. In view of the fact that the use 
of formalin in connection with milk is prohibited by law in 
some places and is usually seriously objected to by health 
officers, it seemed desirable to find some other method for 
sterilizing the machines without the use of the formalin so- 
lution. 
