90 REPORT OF DEPARTMENT OF BACTERIOLOGY OF THE 
doubtedly due to some factor other than the absence of cotton 
in the suction filter. 
These results indicate that where the dairyman does not 
feel that there is sufficient time to fill all of the filter cups 
with cotton the maximum benefit will be obtained by filling 
the suction filter. 
Absorbent vs. ordinary cotton in the filter cups.—In some 
of our earlier work with the milking machine the cotton used 
in the filter cups was that known as absorbent cotton, it having 
been treated chemically to remove the oil and other foreign 
substances. On account of its previous treatment this cotton 
is much more expensive than the ordinary form and it has 
some other disadvantages. The difficulty of removing all of 
the moisture from the earlier form of filter cups has been 
mentioned and this form of cotton readily absorbed this moist- 
ure and tended to mat down and interfere with the passage 
of air. A. comparison was made of the relative: filters in , 
efficiency of absorbent and ordinary cotton. . 
In this, the milking parts were kept in brine, the same man 
operated both machines, the vacuum was released through the 
teat cups and the conditions were made as strictly comparable 
as possible except that at each milking the filter cups of each 
machine were packed with the two kinds of cotton respectively. 
The results from this test are given in Table XI. 
