The origin of some of the streptococci found in milk / by L.A. Rogers and Arnold O. Dahlberg, Dairy Division, Bureau of Animal Industry.

  • Rogers, L. A. (Lore Alford), 1875-1975
Date:
[1914?]
Catalogue details

Licence: In copyright

Credit: The origin of some of the streptococci found in milk / by L.A. Rogers and Arnold O. Dahlberg, Dairy Division, Bureau of Animal Industry. Source: Wellcome Collection.

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    rapidity and after three days there was no question that the cultures were able to utilize glycerin. Those represented by the curve D, on the other hand, produce only a very slight increase in acidity, which even at the end of 14 days is only slightly above 1 per cent normal. Between these two is a third group in which there is a slow but dis¬ tinct increase in acidity. At seven days the acidity is above 1 per cent normal. While an error may be introduced in some cases by drawing the line between fermentation and no fermentation of glycerin at 1 per cent normal, it is believed that in these results this error will be slight. These results illustrate the value of the exact results obtained by titra¬ tion which we have always used in preference to the simpler and more rapid way of determining the change of reaction with litmus in solution in the broth or with litmus papers. We also consider it a decided advantage to allow sufficient time for the completion of the fermentation, thus securing an end point rather than some intermediate and varying determination. Seven days are not sufficient for the completion of the glycerin fermentation, but it is undoubtedly ample for other test substances which we have used. Table I.—Progressive fermentation of dextrose and glycerin. Dextrose. 0.15 0.19 0.31 0.34 0. 44 0. 55 0. 58 0.91 0. 53 0. 96 0. 78 1.21 • 2K • 23 . 80 1.67 1. 31 3- 6S 2. 73 4.96 4- 85 4. 96 5-43 eh. . 22 . 46 ■ 35 i- 57 I- 54 2. 40 2. 38 3- 96 5. 06 4. 61 3- 74 4- 68 • is . 14 • 37 • 37 . 96 .86 . 28 • 63 I- 83 . 92 •33 I- 13 •OS • 59 .82 •95 1. 09 1. 30 I- 49 2. 16 i- 73 2. 18 2. 30 2. 63 ev . • 15 . 09 • 34 • 17 • OO . 40 •45 . 66 i- 03 . 96 • 70 1. 18 hw. . 20 . 11 .67 •95 I. 07 i-35 1. 67 1-38 2. 08 2. 71 2-45 3- 15 • 15 • 20 . 00 • x4 . 00 • OO • 25 . 02 •3i •43 • 76 • 21 • 29 • 04 . 00 • 05 • 03 . 00 . 01 . 00 . 21 . OO . 11 • 09 • 02 .07 . 09 •05 . 02 . 11 . 48 . 46 • 03 om. • 15 .00 . 09 . 11 . 09 . 06 . 00 . 21 • 13 • 19 • OO . OO • 05 . 09 • 22 •32 • 24 •36 •31 • 71 • 53 • 76 . 66 • 78 THE CORRELATION OF PHYSIOLOGICAL CHARACTERS The complete results of the tests made on this collection of cultures are presented in Table II. The reduction of neutral red and the curdling of milk are given in the table, but are not used in the correlations. Adonite and dulcite are necessarily excluded, since these cultures almost without exception fail to ferment these two substances.