BACTERIA AND THE BURRELL-LAWRENCE-KENNEDY 



MILKING MACHINE. 



By S. F. Edwards, Professor of Bacteriology. 



Our investigation with the Burrell-Lawrence-Kennedy milker was of 

 brief duration. The object was only to determine whether pure milk could 

 be obtained with the machine milker under conditions that would make its 

 use practicable upon the farm. 



No attempt was made to determine the species present in the samples 

 beyond the detection of acid producers and those which liquefy gelatin. 

 Milk produced under even more cleanly conditions than usual, either by 

 machine or hand milking, will contain a varying number of species of 

 bacteria. Of these, the acid-producing organisms are largely lactic acid 

 bacteria, which only sour the milk and are harmless. Organisms which 

 can liquefy gelatin can cause a chemical disintegration of the nitrogenous 

 constituents of the milk, visible to the eye in old milk, as a liquefaction of 

 the curd. During this process products may be formed which are poi- 

 sonous to the body, causing gastro-intestinal disturbances. Aside from 

 the acid producers and liquefiers, other species may be present, some 

 inert, while some, alone or in associative action with others, are apt to 

 produce objectionable odors or flavors in milk, or its products, butter 

 and cheese. Disease-producing organisms may be present if the animal 

 is diseased. 



As bacteria are always associated with dirt and filth, the bacterial 

 flora of milk, either machine or hand drawn, will depend upon the clean- 

 liness of the surroundings where the milk is secured. 'In this connection 

 it may be said that the conditions existing in the College dairy barn are 

 far better than those which prevail upon most farms. 



The Cleanliness of the Milking Machine. From the time the milker 

 was installed until after the test began, a period of about seven months, 

 the machine was cleaned according to the directions issued by the manu- 

 facturers. The first samples were taken as the milker was ordinarily 

 operated, the cows being milked by machine and by hand on alternate 

 days. The results are shown in Table I. 



As seen by a glance at the table, every sample of machine-drawn milk 

 showed a very high bacterial content, while most of the hand-drawn 

 samples showed b. bacterial content comparatively low. In the production 

 of "sanitary" or "certified" milk in cities, the standard established by 



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