152 CITY MILK SUPPLY 



receives at milking can be prevented by the use of the small-top pail. 

 A defect in many of the covered pails is the lack of a ridge around the 

 opening to prevent dirt rolling from the top of the pail into the milk. 



Milking Machines. The drudgery of milking has deterred many a 

 farmer from entering dairying and the increasing cost of farm labor has 

 made employers anxious to economize in its employment. So of recent 

 years there has been much experimenting with milking machines. As 

 early as 1819 inventors were endeavoring to produce a successful me- 

 chanical milker but it was not till the appearance of the Lawrence- 

 Kennedy machine in 1902 that a measurably successful one was pro- 

 duced. Since that time advance has been rapid and at the present time 

 there are several milkers on the American market; among them are the 

 Burrell-Lawrence-Kennedy or B-L-K, the Sharpies, the Calf-way and 

 the Empire. Harding has pointed out that these and all other successful 

 machines operate on the suction principle, imitating the calf which wraps 

 its tongue around the teat, presses it slightly and forms a vacuum thereby 

 producing a suction which releases the sphincter muscle of the teat and 

 withdraws the milk. The calf does not suck steadily but gives about 40 

 sucks a minute so that the application of the vacuum is intermittent. 

 In the early machines the vacuum was continuous and it was not till 

 Shiels conceived the idea of admitting air to produce vacuum pulsations 

 that encouraging results were obtained. This idea was perfected by 

 Lawrence and Kennedy. 



It has been the object of manufacturers to produce milkers of low first 

 cost which should be economical and simple to operate, which would not 

 injure the cows, which would milk so clean that it would be unnecessary 

 to milk out the strippings by hand and which would deliver milk of low 

 germ content. Varying degrees of success have attended the efforts to 

 attain these results. With regard to the production of sanitary milk, 

 the machines were at first a great disappointment but at the several 

 experiment stations where they were installed for study showed that the 

 principal sources of contamination were: (1) the air that was admitted 

 to the teat cup; (2) the soiling of the cups by careless handling and drop- 

 ping them on the floor; and (3) the rubber parts which were difficult 

 to clean after milking. 



The air contamination was easily prevented by filtering the air through 

 cotton before admitting it to the cups. The contamination that results 

 from dropping the cups can be avoided only by handling them carefully 

 in the stable. The contamination from the imperfectly cleaned rubber 

 parts was difficult to cope with. It was soon seen that the parts would 

 not only have to be thoroughly washed but that they would have to be 

 kept when not in use in some antiseptic solution. After considerable 

 experimentation common salt, lime water and bleaching powder have 

 been found suitable for the purpose. The common practice now is to 



