BACTERIA IN BUTTER. 211 



penetrate. The conditions in the butter are certainly un- 

 favorable to the continued existence of bacteria, for they 

 begin to die very quickly and they diminish with great 

 rapidity. Freshly made butter will contain millions of bac- 

 teria per gram, but if the same butter is examined from day 

 to day the number is seen to diminish rapidly. The follow- 

 ing figures of a single sample of butter illustrate this rapid 

 decline. 



NUMBER OF BACTERIA PER GRAM OF BUTTER. 



Two hours old 50,000,000 



One day old 26,000,000 



Four days old 2,000,000 



Thirty days old 300,000 



This rapid decline of bacteria is found in practically all 

 samples of butter that have been tested and may, therefore, 

 be looked upon as the normal history of .the bacteria after 

 the butter is made. It is, of course, evident that a large part 

 of the butter will be consumed before the bacteria have 

 become very greatly reduced, and even butter which has been 

 preserved for many months is found to contain small num- 

 bers. The consequence is that in consuming butter the pur- 

 chaser is always swallowing bacteria in comparatively large 

 numbers. 



The salting of butter has a checking action upon bacteria 

 growth and aids in preserving butter from their action. 

 Butter that is made without salting does not keep so readily 

 as salted butter, and the evidence indicates that this is due to 

 the fact that, under these circumstances, bacteria grow more 

 readily. 



Certain pathological bacteria may possibly find their way 

 into butter, and can remain alive for some time. The typhoid 

 bacillus and the tuberculosis bacillus are capable of living for 

 many days in butter and this product, therefore, may pos- 

 sibly be a source of these two diseases in the consumer (124). 

 Although this is certainly a theoretical possibility, there is no 



