216 



SCIENTIFIC AGRICULTURE 



Mai-ch, 1922. 



under examination at each of the four cen- 

 tres at present included in our investiga- 

 tion, has led us to inquire further into the 

 phenomenon. The varying periods occu- 

 pied in the 'clotting" of the milk we exam- 

 ined are given herein on Page 214. From 

 unpublished laboratory data we record that 

 at Centre "A'", dissolving of the clot had 

 begun within 24 hours in 26 of the 28 sam- 

 ples; at Centre "B", 31 of the samples 

 showed partial dissolving of the clot witli- 

 in 24 (hours; at Centre "C", 128 of the 

 140 samples were dissolving within 24 

 hours: and at Centre "D", 11 samples had 

 commenced to dissolve in 24 hours. 



A Detailed Study — Centre "A". 



In pursuit of our enquiries relative to 

 the phenomenon of "dissolving" or "pep- 

 tonizing'" we selected centre "A" for fur- 

 ther investigation. 



Nitrate broth 

 Broth for Indol Test 



Standard Methods (27) 

 Standard Methods (27) 



Media Employed: 



Beef-peptone-agar 

 Beef -peptone -gelatin 

 Beef -peptone-broth 



Standard Methods (27) 

 Standard Methods (27) 

 Standard Methods (27) 



Reaction of Media.. The media was ad- 

 justed according to hydrogen-ion concen- 

 tration, so that the final reaction was 

 PH=7, using brom-tliymol-blue or phenol- 

 red as indicator. 



Milk — Fresh milk was separated, tubed, 

 and sterilized by heating in flowing steam 

 for thirty minutes on three successive daj'S. 



Litmus Milk — prepared as above — see 

 Milk — with the addition of sufficient azo- 

 litmin solution to give the desired blue 

 color. 



Milk -\- Peptone — prepared as above 

 — see Milk — with the addition of 1% 

 peptone (Difeo.) 



Sugar-broths — Broth consisting of pep- 

 tone (Difco) 1% sodium chloride 0.5%, 

 and water 98.5%, was prepared, tubed — 

 Dunham tubes being inserted for the col- 

 lecting of the gas — and sterilized for 15 

 minutes at 15 lbs. pressure. The carbo- 

 hydrates used were made up separately as 

 10% solutions in distilled water and ste- 

 rilized as above. The carbohydrate solu- 

 tions were then added to the broth in such 

 proportion tliat the final broth contained 

 .5% of the required carbo-hydrate. Prior 

 to inoculation the broths were incubated 

 for 48 hours at STVij deg. C. in order that 

 any contamination might be detected. 

 Brom-thymol-blue was used as indicator. 



In June and July, 1920, series of sam- 

 ples of material for examination were 

 taken. Observing the necessaiy precau- 

 tions, milk was drawn direct from the ud- 

 der into sterile test-tubes, the samples being 

 obtained at successive intervals during the 

 milking operations. In this manner, exa- 

 minations were made of the milk of ele- 

 ven individual cows. Samples of the mix- 

 ed milk of the entire herd of thirty cows, 

 of the water used for the washing of the 

 utensils, of the water from the bottom of 

 the tanks in which the utensils were wash- 

 ed, of the water left in the milking mach- 

 ine, of the butter and of the buttermilk 

 starter were taken. Agar plates were ex- 

 posed to the air of the dairy, dairy barn 

 and feed room. Small portions of the 

 grain, ensilage, and hay used as feed, and 

 of straw used for bedding were procured, 

 and inoculated direct into sterile milk. 

 Samples Avere plated on beef-peptone-agar. 

 Milks and agar plates were incubated at 

 37i/> deg. C. and room temperature res- 

 pectively. The results of the fermenta- 

 tion tests were found to be almost identical 

 at both temperatures, except that the dis- 

 solving tended to be more rapid at STi/o 

 deg. C. Of the fortj'-one milks submitted 

 to the "clotting" test, thirty-six showed 

 dissolving within from twenty-four hours 

 to one month. The sterile milks inoculated 

 with feed and straw dissolved. The work 

 done was qualitative. One hundred and 

 thirty-three cultures of organisms which 

 dissolved the casein of milk to a greater or 

 lesser extent were recovered from the var- 

 ious sources enumerated. Fiftj'-seven of 

 the dissolving organisms* isolated, were 

 from the milk samples produced under 

 aseptic conditions; some were recovered 

 from samples taken during the early stage 

 of milking, some from the middle milk, 

 and some from the strippings. 



Of the one hundred and thirty -three 

 cultures, fifty-three appear to be lactic 

 acid producing bacteria. For convenience 

 we place these fifty-three cultures as 

 Group 1. In milk, each strain produces 

 a firm clean clot which begins to show dis- 

 solving in from one to seven days. Usual- 

 ly the dissolving begins at one side of the 

 tube, extending throughout the entire 



