New YorK AGRICULTURAL EXPERIMENT STATION. 63 
broken at the close of the milking. In the earlier form of 
machine the introduction of material from this source was so 
great that at times the milk was noticeably colored with iron 
rust. The work of Prof. Stocking pointed out that this was 
also an important source of bacterial contamination and the 
main suction filter was an immediate result. The relief filters 
for the purpose of removing the germs from the air before it 
entered the machine came later as a logical extension of the 
Same idea. , 
The introduction of these filters, which removed the germs 
from the inflowing air in proportion to their efficiency, was 
the second important step in the development of the sanitary 
milkizg machine. Later progress has consisted mainly in per- 
fecting the ideas embodied in the application of the salt solu- 
tion and the cotton filter. , 
Hastings and Hoffman® studied the germ content of milk 
obtained with the Burrell-Lawrence-Kennedy machine and con- 
trasted it with the milk drawn by hand from other cows. This 
milk was drawn by hand into a 12-inch pail. The rubber parts 
of the milking machine were kept in lime water. The resulting 
numbers showed rather wide fluctuation in the germ content 
with both methods but on the whole were rather in favor of the 
machine. The keeping quality of the milk obfained was not 
influenced by the manner of milking. Woll and Humphrey’ 
made careful tests of the same machine for twenty months with 
twenty-nine cows to determine its efficiency, economy and in- 
fluence as used experimentally and by practical dairymen in 
Wisconsin. They concluded that “the success of the milking 
machine will depend largely upon the man operating the ma- 
chine and on his attitude toward milking machines. If the 
machine is given a fair trial and the directions of the manu- 
facturers are carefully followed the machine milking will, as a 
general rule, be a success, at least to the extent of approximat- 
° Hastings, E. G.. and Hoffman, C. Bacteria] content of machine-drawn 
and hand-drawn milk. Wis. Agr. Exp. Sta. Ann. Rept. 24: 213-222. 1907. 
See also Centbl. Bakt. wu. Par., IT, 22: 222-231. 1908. 
*Woll, F. W., and Humphrey, G. C. Milking machine experiments. Wis. 
Agr. Exp. Station Bul. 173. Feb. 1909. 
