524 



STATE BOARD OF AGRICULTURE. 



I b. COMMENTS. 



Bacteriological workers -with lactic bacteria have often met with inconsistencies 

 in their lactic cultures which would not yield to satisfactory explanations and 

 perhaps have felt many times that all factors and circumstances have not been 

 brought to light. Lactic micro-organisms in pure cultures do not always behave 

 the same, and they do not even when introduced into unsterilized milk. Whether 

 the recognized irregularities may be attributable wholly to association the future 

 must determine, but there will be manifest in these investigations other elements 

 which should enter at least for consideration and may eventually become known 

 influencing factors. Because of this possibility, considerable discussion and many 

 data will follow, treating of some of the many forces at work. 



Lactic micro-organisms grow slowly and irregularly in milk during the early 

 stages of a culture and vary in cultures in which different milks have been em- 

 ployed. AVhether this is due to the small number striving for foot-hold, or 

 whether it is due to some inhibitive property of the milk, may be guessed partly 

 from what is known of the germicidal action of fresh milk, of the enhanced 

 value of partly digested milk for the cultivation of these germs, and of the great 

 variability -of milks in their response to bacteria. So pronounced are these 

 factors at times that one is led to suspect that the nitrogen of milk may not 

 be in the most suitable form for germ feeding, or the constituents of milk are 

 not favorable to rapid development of germ life, or, perhaps, anti-bodies are 

 present. These facts are established, however, as shall be seen later: All diges- 

 tions are not able to furnish the products needed, for it will be found that a 

 large percentage of milk peptonizing germs will prove worthless in fostering 

 the souring of milk by favorably influencing lactic germs, on the other hand 

 it is safe to anticipate a considerable influence exerted by the products of diges- 

 tion upon the growth of lactic germs (a theme which will receive special atten- 

 tion) and upon the wholesomeness of milk (a subject we shall not discuss much in 

 this paper) since the products are stable and will withstand heating; moreover, 

 pasteurization and sterilization would not necessarily check in any way the 

 action of these products If they are capable of inducing gastro-intestinal disturb- 

 ances; the inhibitive or germicidal action of fresh milk is now fairly understood 

 so far as its effects are seen, and while of no great practical meaning, it cannot 

 be disregarded in these investigations; the marked influence different milks 

 have upon the growth of germs is largely a matter of future determinations, still 

 there is sufficient evidence offered in this article to regard it as a very important 

 factor which is involved in nearly all milk studies. 



I. C. REVIEW OF PREVIOUS PERSONAL WORK. 



A cursory review of our own work which has already been published will be 

 necessary to a comprehensive understanding of the entire field and the establish- 

 ment of an existing continuity in the investigations. 



It has been shown that germ B in association with germ A hastens the souring 

 of milk over that produced by germ A in pure culture. This may be easily illu- 

 strated: 



(a) By the naked eye appearance of the milk culture in which loppering oc- 

 curred about ninety-six hours earlier in the combined culture A + B* than in a 

 pure culture of germ A. In litmus milk the changes in the litmus may be fol- 

 lowed more easily than the curdling, for the formation of acid is far more rapid 

 in culture A -|- B, accordingly the litmus notes its production and progress. 



(b) By studying the acidity of cultures A and A -|- B comparatively. 



hours 

 24 hours 

 44 hours 

 68 liours 

 92 hours 

 llt> hours 

 142 hours 



after inocubtion. 

 after inoculation, 

 after inoeuhition. 

 after inoculation, 

 after inoculaticn. 

 after inoculation, 

 after inoculatiun. 



•Culture A -I- B represents a mi.xcd culture in which are found germs A and B in equal ataounta of twenty-four bouillon culture 

 of each. 

 fLdiipcred. JLoppering. 



