156 Bacteria in Market Milk. 



tances, it is obvious that when it finally reaches the consumer it 

 must contain tremendous numbers of microbes of various kinds. 

 The author counted in the market milk of Munich from 13,000 

 upwards to several millions of bacteria per c. c. 



Milk offers to most bacteria which may contaminate it a 

 splendid culture medium, their multiplication in it depending 

 on the character of the container (cans, flat or open bowls), 

 temperature and subsequent treatment. 



Freudenreich, B. Meyer, Cnopf and others conducted experi- 

 ments on the influence of cooling on the number of bacteria, and 

 established definite proof for the statement made in practice that 

 immediate cooling constitutes the best preserving agent for milk. 



According to Cnopf the multiplication at deg. C. was re- 

 markably low, at 12.5 deg. it was 4 to 935 times greater, and at 

 35 deg. 2,200 to 3,800 times greater than at deg. C. 



Freudenreich proved that in milk which at the beginning of 

 experiments contained 10,000 (accurately 9,300) bacteria, they 

 scarcely multiplied when kept for three hours at 15 deg., w T hereas 

 at 25 deg. they doubled, and at 35 deg. they tripled in quantity. 

 After six hours at 15 deg. they numbered 2.7 times, at 25 deg. 

 18.5 times, at 35 deg. about 1,300 times more than the original 

 number, while after nine hours the number when kept at 15 deg. 

 was 5 times, at 25 deg. 108 times, at 35 deg. 3,800 times as numerous 

 as in the original count ; and in 24 hours at 



15 deg. C. the count was 5,700,000, or 613 times 

 25 deg. C. the count was 50,000,000, or 5,380 times 

 35 deg. C. the count was 570,500,000, or 61,344 times 



The author desires at this place to comment especially on the slight, and -somewhat 

 problematical value of bacterial counts, not alone because the results of the different 

 sowing and counting methods show such enormous differences, but because the entire 

 system also depends on a supposition of the development of a colony from a single 

 bacterium which was previously present, a premise which is open to very serious 

 objections. If it is considered how many bacteria attach to tenaciously adhering 

 threads (sarcina, streptococci'), and how many bacteria possess a tendency to proliferate 

 in cultural combinations, and to remain together in the relatively sticky material of 

 milk, then it becomes apparent that the counted bacterial number represents but a small 

 part of the number of bacteria which are actually present in the milk. Of course in 

 general the number of colonies developing on the plate represent a certain initial 

 point for deducing whether and in what degree a bacterial growth has taken place in 

 the milk, but it does not indicate more than the relative age of the milk, since fresh 

 milk may also be rich in bacteria, and besides luxuriantly growing as well as slowly 

 multiplying bacteria may be present in the milk. 



A better method for the establishment of the actual number of bacteria in milk is 

 the one suggested by Skar, which consists of a direct count of the bacteria in a smear 

 (see technique). 



Through plating a certain impression is obtained of the kind 

 of bacteria occurring in the milk, and corresponding to the growth 

 of the colonies and the morphology of the bacteria it is possible 

 to draw certain conclusions as to the groups under which the 

 bacteria that are present may probably be classified. 



Further deductions as to whether the microbes should be con- 

 sidered pathogenic, and whether bacteria are present which confer 



