EXPERIMENT STATION WORK RELATING TO PURE MILK. 289 



materials were found to be good bedding materials in sanitarj^ dairy- 

 ing. Cut corn fodder was considered better and more economical 

 than wheat straw where both crops are grown primarily to secure 

 bedding material. 



MILKING. 



The OTeatest contamination of milk occurs usually at the time of 

 milking. The conunonest forms are particles of dust from the air 

 of the stable, which are especially numerous when cows are bedded or 

 fed just before milking; filth from the udder and adjoining regions 

 of the cow, loosened by the movements of the animal and the manipu- 

 lations of milking; and impurities from the hands and clothing of the 

 milker. Along with every particle of dirt gaining access to the milk 

 are, of course, multitudes of bacteria. 



Fraser " made some observations on the amount of dirt falling from 

 udders designated as apparently " clean,"' '' soiled," and " muddy." A 

 glazed dish having about the same diameter as an ordinary milk pail 

 was held under a cow's udder for four and one-half minutes, the aver- 

 age time which it had been found in a number of trials to be required 

 to milk a cow. During this time the milker went through motions 

 similar to those made in milking, but not drawing any milk. The 

 dirt thus collected was approximately the same as would have fallen 

 into the milk during the milking process. Seventy-five trials were 

 made at different seasons of the year, the average results showing 

 that 0.0152 gram of dirt fell from udders apparently clean, 0.1316 

 gram from udders slightly soiled, and 0.8831 gram from nuiddy 

 udders. It was therefore estimated that in 32 milkings the 275 

 pounds of milk produced would contain 1 ounce of filth where the 

 udders were mudd}'. After these tests the udders were washed and 

 the dirt collected in the same manner as before. The amount of dirt 

 collected before washing as compared with that after washing was 

 3i times as great in the case of udders apparently clean, 18 in the 

 case of soiled udders, and 90 where the udders were muddy. 



In the same bulletin Fraser reports observations on the number of 

 bacteria gaining access to milk under ditferent conditions. Petri 

 dishes having an area of 63 square centimeters were exposed under 

 different conditions with a view to ascertaining the effect of some 

 of the different operations commonly performed in dairying upon 

 the bacterial content of the milk. The average number of colonies 

 which developed in tlie culture medium for different exposures was 

 as follows: Exposure made in the open field, 0.9; barnyard, 13; well- 

 kept barn during milking, 32: poorly-kept barn during milking, 168; 

 before feeding, 46; after feeding, lOi); after brushing cows, 307; 



"Illinois Sta. r.ul. 1)1. 

 II. Doe. 024. 5l)-l 19 



