4 BULLETIN" 642, IT. S. DEPARTMENT OF AGRICULTURE. 



square feet of light for each cow. Five hundred cubic feet of air 

 space was provided for each cow. An untrained milker, wearing 

 ordinary work clothes and giving no special attention to the cleanli- 

 ness of his hands, was employed to milk and take care of the cows. 



During the work the cows were alternated from time to time in 

 order to equalize any unusual results due to the individual animal. 

 For example, in working with the small-top and open pails two cows 

 were milked first into the open pail and a few days later were milked 

 into the small-top pail. 



In all the work the milk was poured unstrained into cans in the 

 barn. The small-top pail used in the experiments was the type with 



Fig. 1. — Experimental barn used in this investigation. 



a hood or cover on an ordinary pail, as shown in figure 2. Utensils 

 were sterilized by being placed in a sterilizer, steamed for 30 minutes, 

 and afterwards allowed to remain there until used. When the uten- 

 sils were not sterilized they were merely washed clean and inverted 

 in the milk house. Covers were not placed on the cans, and the 

 utensils were left in that position until time to milk. 



Sterile utensils in the strict sense of the term means their absolute 

 freedom from living organisms. When the statement is made that 

 utensils were sterilized it means that they were free from all bacteria 

 which are destroyed by flowing steam at 100° C. (212° F.). There 

 are, of course, a few spores which are resistant to flowing steam and 

 which can be destroyed only by steam of high temperature under 

 pressure. 



