466 



STATE BOARD OP AGRICULTURE. 



after exactly 24 hours, with the exception of F which acidified so slowly 

 that the first test was made after 36.5 liours, the second after coagula- 

 tion at GO hours. All results are compiled in the following two tables. 

 The first one gives the numbers of bacteria and the acidities of the 

 stock culture A at difl"erent days, the second shows the development of 

 the sub-cultures. 



TABLE XL— r/ie Ageing of Culture A of Strain a. 



Age. 



1 day. 



2 days 



4 days 

 7 days 



10 days 



13 days 



Cells per cc. 



1,120,000,0001 

 1.140,000,000} 

 l,150,000,000j 



870,000,000 1 

 &82.000,000 I 

 889,000,000 f 

 980, 000, 000 J 



550.000,0001 

 594,000,000/ 



127,000,0001 

 131,000,000/ 



1,960,0001 

 2,300,000 [ 

 2,490,000 r 

 2,700,000j 



3,500,0001 

 3,700,000/ 



.4eidity. 



09.5° 



100.0° 



108.0° 

 114.0° 



110.0° 



Table XII shows plainly a reduction of the fermenting capacity as 

 well as of the power of multiplication. The fermenting power of the 

 average cell is reduced to about one-third lor one-fourth of that of the 

 original culture in good physiological condition. The rate of multiplica- 

 tion is not so very much affected at first, but after 7 days it is very 

 evident and after 13 days, the cells seemed hardly able to grow at all, 

 one cell after being transferred into fresh milk requiring 8 to 10 hours 

 for dividing. Since both the fermenting power and the reproductive 

 power are thus reduced to about one-fourth of their original activ- 

 ity, the efficiency of the old starter will be only one sixteenth of that 

 of the fresh starter. 



In looking at the colonies of the lactic bacteria on the gelatin count- 

 ing plates, it was easy to be seen that not all cells had been affected 

 in the same degree. The folates of young, vigorous cultures show all 

 colonies fairly large and of the same size within three days. This is 

 not at all true with the old cultures, the size as well as the rapidity of 

 development is entirely different. As an illustration of this may be 

 given the data from the plates of culture A, 13 days old. These plates 

 were counted after 3 days and the duplicate plates showed 63 and 72 

 colonies of fairly good size. After 7 days, they were looked over again 

 and a great number of all sizes of colonies, from the ordinary full 

 size to hardly visible ones was found. Counting all that could possibly 

 be seen with' the naked eye, 3,500 and 3,700 were found on the duplicate 

 plates. 



This experience makes the exactness of counting doubtful, at least 

 with old cultures. There will be perhaps a large number of colonies 



