GROWTH OF BACTERIA IN NORMAL MILK. 27 



are common, for the reason that in all the columns the numbers 

 are not exact but only approximate and, except when very- 

 small, are given to the nearest tens, hundreds, or thousands, 

 as the case may be. 



In the second table the figures in the different columns show 

 what proportion the numbers of bacteria of the various species 

 formed of the total number of 'bacteria present. These per- 

 centages are calculated not from the approximate numbers 

 given in the first table, but from the numbers actually found. 

 They therefore vary slightly, in some of the columns, from 

 the percentages that would be calculated from the first table 

 because of the fact explained above that the figures in the first 

 table are given only in round numbers. 



It appeared to us that the figures in the second table are 

 fully as significant as those in the first, since the percentages 

 alone show the development of the different bacteria as com- 

 pared with each other. If, for example, a given species of 

 micro-organism should remain in the milk during the whole 

 period of experimenting, with only a slight increase in num- 

 bers, the first table would always show an increase during the 

 period of experiment; the second table would, however, show a 

 constant decline, meaning of course that the percentage of the 

 species in question was becoming constantly less as the other 

 bacteria were increasing during the experiment. On the other 

 hand, a species that showed a constantly increasing percentage 

 would be one which would of necessity have an important influ- 

 ence upon the milk. 



In the tables which are here given the bacteria tabulated in 

 the first eight columns are those which we have found present 

 with a very considerable degree of constancy in all samples of 

 milk. The species in question may be briefly mentioned as 

 follows: 



B. acidi ladici. This is the species described by Esten in a 

 previous report.-'^ It has been found by many bacteriologists 

 and is widely distributed in this country. It is apparently 

 identical with B. acidi paralactici described by Kozaif as the 

 most common lactic organism in Europe. It is the species 

 which \ve find with the greatest uniformity in milk, and the 



* Stons Expt. Sta. Rept. 1S96, p. 44. 

 tZtschr. f. Hyg. XXXVIII. 3S6, 1901. 



