62 Report’ OF DEPARTMENT OF BACTERIOLOGY OF THE 
common salt (NaCl). ‘This improvement in the manner of 
keeping the rubber parts was the first step toward the produc- 
tion of milk of an acceptable quality and marks the beginning 
of the real solution of the problem of a sanitary milking ma- 
chine. . 
The suggestion of this idea was due to some earlier observa- 
tions of Mr. D. H. Burrell* on the preserving effect of salt solu- 
tion coupled with the common knowledge of its antiseptic ac- 
tion on putrescible substances. The accurate determination of 
the prime sanitary importance of salt solutions in connection 
with a milking machine is unquestionably due to Prof. 
Stocking. | 
When care was exercised in connection with the machines 
he found it was not difficult to produce milk at the first dairy 
which was of lower germ content than that produced by hand 
milking. On the other hand it was difficult to accomplish this 
at the other dairy on account of the unusually low germ con- 
tent of the milk drawn by hand. The air filters had not been 
added to the machines at the date of this study. 
Stocking and Mason’ reported additional results from a 
study of the Burrell-Lawrence-Kennedy machine. ‘They tested 
the efficiency of lime water and of solutions of borax, of for- 
malin and of salt as a means of keeping the rubber parts in a 
satisfactory sanitary condition. With the exception of the 
tests where the rubber parts were kept in a formalin solution 
the results with the machines were not as good as those ob- 
tained at the same time by hand milking. During the progress 
of these studies the air filters were added to the machines but 
they were not then as efficient as the forms which were later 
devised. 
The use of a cotton filter in connection with the milking 
machine was originally suggested by Mr. Loomis Burrell 
as a means of preventing the rise of moisture into the 
vacuum pipes and its return at the time the vacuum was 
‘From correspondence with Mr. Loomis Burrell. 
‘Stocking, W. A., Jr. and Mason, C. J. Milking machines. Part I. 
Effect upon quality of milk. Stoors Agr. Exp. Station Bul. 47. May 
1907. Also Storrs Ann. Report, 19: 105-129. 1907. 
