144 BACTERIA IN MILK. 



The Souring of Milk during Thunder Storms. The only natural 

 agent that causes souring is the growth of microorganisms. There 

 is, however, a wide-spread belief that thunder storms will sour and 

 curdle milk. This belief rests upon a mistaken interpretation of 

 observed facts. It is certainly true that milk is frequently found 

 sour after a thunder storm, and the natural interpretation is that 

 the electricity of the storm has produced the souring. A careful 

 study of the phenomenon has shown that this inference is incorrect. 

 Electricity, in the form of a current or electric sparks, has no power 

 to sour milk; and, further, if milk is kept properly cooled, the thunder 

 storm has no effect upon it. Moreover, if milk has been deprived 

 of bacteria, it will keep indefinitely, remaining sweet in spite of 

 thunder storms. In short, all evidence shows that the thunder 

 storm has no power of souring milk, unless bacteria are present to 

 produce the lactic acid, and that thunder and lightning have no 

 direct effect upon the souring of milk. 



What, then, brings about the frequent souring of milk during 

 thunder storms and the wide-spread belief that thunder is the cause ? 

 The answer seems to be the simple one, that the same agencies 

 which produce the thunder storm cause a rapid growth of bacteria. 

 The thunder storm is brought on by climatic conditions, dependent 

 chiefly upon the temperature, and these same conditions are just 

 those that stimulate bacterial growth. It will thus happen that the 

 same sort of warm weather which produces the thunder storm also 

 hastens the growth of bacteria in milk if not kept artificially cooled 

 with ice. It will frequently happen, as a result, that the milk will 

 be ready to show signs of souring at the same time that the thunder 

 storm appears, frequently in the afternoon. The two phenomena 

 occur together, not because the one causes the other, but because 

 the same climatic conditions which produce the storm hasten the 

 growth of bacteria. A similar warm spell will sour the milk just 

 as quickly, even though no thunder storm appears. Whether this 

 is the whole explanation may be doubtful, but it is clearly demon- 

 strated that the thunder and lightning have nothing to do directly 

 with the phenomenon. The souring of milk is always produced by 

 bacteria. 



