5RICULTURAL 



LIBRARY, 



TION. 



REDUCTION OF BACTERIAL CONTAMINATION. 47 i f 



found, however, for only a single day. In the next sample 

 that was taken the number had dropped down again to the 

 normal average. Of course, there must have been some . 

 extraordinary source of contamination in this case, and if a 

 careful investigation could have been made it would probably 

 have been determined. The example is mentioned, however, 

 as indicating that, even under the best and most careful con- 

 ditions, there will be occasionally unexplained irregularities. 

 This phenomenon has also frequently been noticed by dairy- 

 men ; for, in special dairies, where extreme care is taken and 

 where the milk is in general of a high character, there are 

 occasionally incidents such as that just mentioned. Upon 

 one or two days the milk sours very rapidly, due doubtless 

 to the presence of a much larger number of bacteria than 

 usual, although the conditions under which the .milk has 

 been obtained are, so far as can be determined, identical with 

 those which were found in the dairy upon other days. To 

 what such great irregularities are due we can at present 

 give no explanation. 



HOW TO REDUCE BACTERIAL CONTAMINATION. 



There are no means of avoiding the bacteria from the milk 

 duct; but these form really a small part of the bacteria in 

 ordinary milk, most of which come from external sources. 

 Though the latter cannot be wholly avoided, they may be 

 very greatly reduced in numbers by simple precautions that 

 may be adopted in any dairy (19, 29). In general it may be 

 stated that an increase in cleanliness will result in a reduc- 

 tion of the amount of bacterial contamination ; but in order 

 to understand this statement and its applications it is neces- 

 sary to consider the various points to which attention should 

 be especially directed. They are as follows : 



The Cow. Since the dirt which is allowed to accumulate 

 upon the skin of the cow is one of the largest sources of 

 bacterial contamination it naturally follows that an efficient 



