The origin of some of the streptococci found in milk / by L.A. Rogers and Arnold O. Dahlberg.

  • Lore Alford Rogers
Date:
1914
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Licence: Public Domain Mark

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

    9/28 page 497
    . Mar. 25, ror Streptococci in Milk 497 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. Percentage of normal acid produced in— Culture No. I 2 3 4 5 7 8 9 Io Ir 12 I4 day. | days.| days.} days.| days.| days.| days.| days.] days.| days.| days.| days. 1S RECS CAG GOMOD IO Srna ae ALO Relat aup ee Ooo Bee le cities ar tts iy stakiela delle sci ted evokes URil ee chefs MO, Sah cras zine eee ues 46) 5-0} 5.2 SoS tial Seu ude: cre ati eletere-ainllare tural ican: Cote ateese wl stair tare cists ES ee areasarasaacotals ee aya aedtelabeek Baa AWS 7G tm Osta vii Os Ki. My Oss A Stars: gho/e ts arevadeue atuas Gumi otave a Reali earn ahaha ot Caeei Lick castes GLYCERIN. i Seat ici sis ata « Sn NIAs e's aiataus & O15 | 019 | 0.31 | 0.34] 0.44 | 0.55 | 0. 58 | 0. 91 | 0. 53 | 0.96 | 0.78 I. 22 CRF eet slelece tart insole cvehavel a> 25 23 oO | 1.67] 1.31 | 3.65 | 2.73 | 4-96 | 4-85 | 4.96 ]...... 5-43 Coe, ee eS A ot aero MO Cre, 22 46 35 | 1-57 | 1-54 | 2-40 | 2.38 | 3-96 | 5.06 | 4.61 | 3-74 | 4-68 Coal Ne ne oR eee on see 15 14 37 37 96 - 86 28 63 | 1. 83 92 33 I. 13 Ge F. ach aitee se talepocer hs enue's 05 59 82 95 | I-09 | 1-30] 1-49 | 2.16 | 1.73 | 2-18 | 2.30 2. 63 Vay etch) ciate oistos vintaistene etalaseyely 15 09 34 17 00 40] -45 66 | 1.03 96 70 1. 18 BMWS es hate aatce Seas ne 20 II 67 95 | 1-07 | 1-35 } 1-67 | 3-38 | 2.08 | 2.71 | 2.45 3.55 SIE alerts cava the saiptradinelalsie:s stece I5 °9 14 fore) 200 25 02 °3r 43 76 Eh ae f 5 UN aS in COMO MOO SUCH TOPE 20 29 o4 oo | .05 03 | -0o]} .or 00 21 OOM ena OG So tetion Dons ree cet alonloa ates It 09 o2 °7 (oJe) 05 02 Fe | 48 46 O8 tie cose MOLER 5 ci Bb iata'a/a.4ahela crete sie 3:0 alate cle I5 co 09 II o9 06 200 22 13 19 fore) co DIG Datei Helene ainaese alder 05 09 22 32 24 36 32 live 7d 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.
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