212 BACTERIA IN BUTTER. 



direct evidence at the present time that such a course of 

 infection ever occurred, no examples having ever been 

 observed, where there was even a strong suspicion of the 

 distribution of typhoid or tuberculosis, or any other infec- 

 tious disease, by means of butter. While, therefore, we must 

 look upon butter as a possible source of the distribution of 

 some infectious diseases, it must be looked upon as a source 

 in regard to which there is still room for doubt. This possible 

 danger, however, has so strongly appealed to European 

 scientists that they have urged the legal requirement that 

 all cream for butter-making should be pasteurized before it 

 is ripened, for the purpose of removing the possibility of the 

 distribution of tuberculosis and other infectious diseases by 

 means of butter made therefrom. The absence of direct evi- 

 dence of such danger has prevented this suggestion being 

 anywhere receive^ with favor, but it is still being urged. 



DETERIORATION OF BUTTER. 



Butter does not keep indefinitely, but undergoes deteriora- 

 tion due to several different distinct changes. The first of 

 these is simply the disappearance of the peculiar delicate 

 flavor and a'roma .which is found in fresh butter. This takes 

 place very rapidly, and even within a few days after the 

 butter is made there is a very appreciable falling off in the 

 flavor of the butter. The explanation of this is, doubtless, 

 that the flavor and aroma are due, in a measure, to volatile 

 products which pass off from the butter with considerable 

 rapidity. This effect, however, is not very appreciable, and 

 the butter, for a considerable time, remains of a high quality, 

 though not quite so delicate in flavor as at first. 



After this there occurs a series of changes that are much 

 slower in their action and which depend upon a variety of 

 conditions. They occur most readily if the butter is kept 

 moderately warm and exposed to the light and the air, 

 whereas if it is kept cool, in the dark and protected from too 



