32 



BULLETIN 642,, U. S. DEPARTMENT OF AGRICULTURE. 



ent in the milk drawn directly from the udder. It was not found 

 for the reason that the bacterial count being so great such dilutions 

 had to be used in plating that the small number of bacteria of that 

 type did not appear on the plates. It is also of interest to note that 

 the washings from the unsterilized cans contained high percentages 

 of the alkali-forming bacteria and particularly the peptonizing 

 group. The addition of peptonizing bacteria in large numbers to 

 milk is a matter of considerable importance, since they may be highly 

 undesirable in that they produce putrefactive changes. North has 

 frequently called attention to the importance of the use of sterilized 

 utensils, which has been further emphasized by results obtained by 

 Prucha, Harding, and TVeeter (3). The work of these investigators 

 and our own experiments indicate clearly that the use of sterilized 

 utensils is the greatest factor in the production of milk of low bac- 

 terial count. 



Table 14. — Bacterial [/roups in mill: directly from the udder, in fresh milk from 

 sterilized and unsterilized utensils, and in washings from clean but unsteril- 

 ized cans. 





Number 

 of samples 

 averaged. 



Bacterial groups. 



Source of sample. 



Acid co- 

 agulating 



Acid. 



Inert. Alkali. 



Pepto- 

 nizing. 



Acid co- 

 agulating 

 (pepto- 

 nizing). 





47 

 19 

 17 

 2 



Per cent. 



46.21 



25.81 



11.54 



.39 



Per cent. 



37.2.5 



39.22 



16.99 



1.85 



Per cent. 

 9.41 

 25.51 

 31.55 

 11.64 



Per cent. 



0.45 



.71 



14.14 



19.24 



Per cent. 



1.36 



3.26 



25. 79 



66.87 



Per cent. 

 5.09 



Milk from sterilized utensil . . . . 

 M ilk from unsterilized utensils. . 

 Wa-shings from unsterilized cans. 



5.49 











The small dairyman often has difficulty in providing an inex- 

 pensive apparatus for sterilizing his utensils. Realizing this, a sim- 

 ple steam sterilizer has been devised in the Dairy Division. The 

 sterilizer, fully described in Farmers' Bulletin 748, entitled "A Sim- 

 ple Steam Sterilizer for Farm Dairy Utensils," is inexpensive to 

 construct and operate and provides a practical method for sterilizing 

 dairy utensils on a small scale. The bulletin will be sent free to 

 anyone on request to the Department of Agriculture. 



CONTAMINATION OF MILK BY MANURE AND DIRT. 



It has been shown that unsterilized utensils are a source of very 

 great contamination of milk, but they are not the only means of con- 

 tamination. Statements have been made, and possibly it has been the 

 general belief, that the greatest contamination of milk comes from 

 manure and other accumulations of dirt on the body of the cow. 

 The results in these experiments indicate that while that' is an im- 

 portant source of contamination from the standpoint of the number 



