450 



STATE BOARD OF AGRICULTURE. 



The foll(>\viiii> table after Miiller gives the actual iminibers of a cer- 

 tain bacterium . in broth counted at different times. The last column 

 gives the numbers after inoculation by the plate method computed under 

 the supposition that the multiplication had followed the geometrical 

 progression. 



TABLE I. — Actual and Theoretical Increase of Bacterium A at +6° after Muller. 



Time. 



Number 

 of cells 

 found. 



hours . 



4 hours . 



8 hours . 

 12 hours . 

 24 hours . 

 28 hours. 

 32 hours . 

 36 hours . 

 48 hours . 

 52 hours . 

 56 hours . 

 00 hours. 

 72 hours . 

 76 hours . 



1,370 



1,650 



2. 160 



2,860 



8,000 



11,600 



17,500 



27, 900 



79,900 



130,000 



180,000 



273,000 



,353,000 



,956,000 



Number 



of cells 



computed. 



1,370 



2,010 



2.940 



4,310 



13,530 



19,820 



29,000 



42,500 



133,700 



196,000 



287.000 



542,000 



320,000 



956,000 



The retardation of growth is evident, as is also shown in the curves 

 of Fig. I. But this retardation of growth comes at a time when the 

 number of cells is very small. The products formed at this early period 

 of growth are so insignificant in quantity that we cannot detect them 

 by any chemical means. This is easily shown by the following Table 

 II, giving the growth and acid formation of Bact. lactis acidi in milk. 

 The rate of reproduction, i. e. the number of minutes required for one 

 cell to double, is lowest, or the multiplication is fastest when the first 

 traces of acid can be detected chemically. Soon after this point has 

 been reached, the rapidity of growth decreases, slowly at first, then quite 

 rapidly after about 0.3% of acid has been formed. At 0.4% to 0.5% 

 of acid, growth ceases entirely. The table shows that the rate of growth 

 is not constant, and that the retardation of gi'owth in a young culture 

 is overcome by the time the fjroducts can be analyzed. Therefore, the 

 fermenting capacity will not be influenced seriously by the initial re- 

 tardation. As long as the gradual decrea.se of the rapidity of growth 

 is not considered in the mathematical equation, the results will be the 

 more accurate the shorter the period of experiment. 



TABLE II — Growth and Fermentation of Bacterium lactis acidi. 



Time. 



hours 

 3 hours 

 6 hours 

 9 hours 

 12 hours 



15 hours 

 18 hours 

 21 hours 

 24 hours 



271iour? 

 30 hours 

 33 hours 

 36 hours 



Cells per cc. 



38,000 



200,000 



1,710.000 



19,600,000 



113,000,000 



4.35,000,000 

 1,135,000,000 

 1,370.000,000 

 1,550,000,000 



1,3.50.000.000 

 1,300,000,000 

 1,440.000,000 

 1,610,000,000 



Acid 

 per cent. 















0.007 



0.018 



0.086 

 0.263 

 0.434 

 0.479 



0.502 

 0.524 

 0.520 

 0.538 



Rate 

 of growth 

 minutes. 



74.8 

 58.1 

 50.8 

 70.9 



92.2 



130.0 



663.0 



1010.0 



Cells per cc. 



38 



: 183 



1,750 



23,250 



301,000 



4,800,000 



43.200,000 



177.000,000 



685,000,000 



1.240,000,000 

 1,520,000 000 

 1,390,000,000 

 1,750,000,000 



Rate 

 of growth 

 minutes. 



79.0 

 55.0 



52.7 

 48.5 



45.1 

 56.8 

 88.5 

 92.2 



210.3 



619.8 



