PRODUCTION" OF MILK OF LOW BACTERIAL CONTENT. 3 



OBJECTS OF THE INVESTIGATION. 



The objects of the investigation may be outlined as follows : 



1. To work on only fresh milk at the time of milking, in order to eliminate 

 the factor of bacterial growth. 



2. To obtain conditions as bad as possible in an experimental barn in order 

 to improve them and also to determine the number of bacteria in fresh, dirty 

 milk. 



3. To introduce one factor of improvement at a time, so as eventually to 

 obtain milk of low bacterial content. 



4. To return to the dirty conditions and then again produce low-count milk 

 by the application of the necessary factors with the object of checking the 

 value of the factors previously determined. 



5. To show the relative importance of the selected factors. 



6. To use a combination of the essential factors in a practical manner on - 

 farms in order to determine their value when used by the average farmer. 



7-. To show the growth of bacteria in various grades of milk (graded from 

 a bacterial standpoint) when held for different periods of time at various 

 temperatures. 



Since the term " production of milk " is usually considered to 

 cover the entire period in which it is in the farmer's hands, the bac- 

 terial content during production, as used in that sense, must be con- 

 sidered from two distinct standpoints, first, the bacteria introduced 

 through contamination, and second, their growth in the milk. 



In this paper, however, we shall consider the term " production of 

 milk " to cover only the period from the time the milk leaves the 

 cow until it is in the delivery cans or bottles, which includes the 

 time the milk is subject to the usual sources of contamination. The 

 time the milk is held on the farm, will be considered as an entirely 

 different phase of production, since the bacterial content during that 

 period is not usually influenced by contamination, but is subject to 

 increase through bacterial growth. 



Particular attention is called to the fact that extreme conditions 

 of filth were used merely to emphasize the importance of certain 

 factors. No legitimate excuse can be conceived for the production 

 of milk from dirty cattle or in a filthy stable. 



DESCRIPTION OF BARN AND METHODS USED IN THE PRODUC- 

 TION OF THE MILK. 



For the experiments a small barn was constructed at the Dairy 

 Division farm at Beltsville, Md., a view of which is shown as figure 1. 

 The building provided space for four cows and was of wooden con- 

 struction throughout, including floor, gutter, and mangers. The 

 walls were left in the rough; that is, with exposed beams, etc. 

 The loft above the cows was constructed of narrow boards laid from 

 1 to 2 inches apart on crossbeams. From the loft hay was thrown 

 down and the cows fed just before milking. The stable had two 

 doors and two windows ; the latter were small and provided only 2 



