New York AGRICULTURAL EXPERIMENT STATION. 19 
fairly good barn conditions milk with a germ content of 20,000 
to 30,000 per ce. marked the practical limit of this improve- 
ment. nS) 
It will be remembered that after each pulsation of the ma- 
chine air is admitted to release the vacuum and this air being 
drawn from beneath the cow and in close proximity to the 
bedding must carry with it dust and bacteria in considerable 
numbers. The origin of the cotton filter has been discussed in 
connection with the work of Stocking (see page 63) and the 
first machines furnished us by the makers were equipped with 
the small cotton filters shown in Plates V and VI. During 
the period in which this study has been conducted the filters 
have undergone marked improvement and the importance of 
the principle of filtering the air entering the.machine is well 
illustrated by the variations in germ content which have fol- 
lowed the use of these various filters. 
Test of small filters— On the model first studied, machines 
Nos. 1287 and 1288, the relief filter on the pulsator head was 
the same size as those on the teat connectors and all were quite 
small as is shown in Plate V, fig. 1, and Plate VI, fig. 3. In 
these plates the blocks opposite the filters indicate the cotton 
containing capacity of the filter cups. The main suction filter 
{Plate V, fig. 1) was cast in the body of the pulsator at the 
base of the nipple which joins the milker to the stanchion 
hose. It will be noted from the plate that it would :accom- 
modate only a thin layer of cotton. ; 
In the test of these machines the teat cups and rubber parts, 
with the exception of the stanchion hose, were kept in a 10 
per ct. salt solution. The only variation in handling was the 
insertion of cotton in the filter cups during 2 part of the tests 
and the omission of cotton from the filters at other times. The 
milk of three successive pairs of cows was tested to determine 
whether there was such a progressive change in the germ con- 
tent of the milk as was noted in connection with the Globe 
machine. 
The results of this examination are given in Table V, 
