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XXXI. On the nature of Lactic Fermentation, and on an apparent 

 conversion of Caseine into Albumen which accompanied the pro- 

 duction of Lactic Acid in Milk excluded from the Air. By 

 William K. Sullivan*. 



ABOUT four years ago I procured two samples of cow's milk 

 for the purposes of an investigation which I proposed to 

 make upon the influence which age, temperature, food, and other 

 variable conditions exert upon the relative proportion of the dif- 

 ferent fats composing butter. The milk just drawn from the 

 cow was introduced into clean well-stoppered glass bottles, and 

 stoppered in such a way as to leave no air between the stoppers 

 and the milk. Other occupations having prevented me from 

 proceeding at the time with the inquiry, the bottles of milk were 

 put aside in a cool place, not subject to very great extremes of 

 temperature, and only examined during the last month. As I 

 believe that the results of this examination may possess some in- 

 terest in connexion with the composition of caseine and its rela- 

 tion with albumen, and also with some of the interesting expe- 

 riments recently made by M. Pasteur vipon fermentation, I have 

 thought them worth publishing. 



For some time after the bottles had been laid aside, no coagula- 

 tion of the caseine took place. Ultimately it separated in the usual 

 way, leaving a perfectly clear, bluish-green liquor. After some 

 time the coagulum gradually disappeared, leaving only the butter 

 floating through the liquid, which in time became almost colour- 

 less. Granulations also appeared in the butter, some of which 

 rested on the bottom of the bottles, and others attached them- 

 selves to the glass. No further change was noticed in the ap- 

 pearance of the contents of the bottles, which remained, however, 

 unopened for about two years after the formation of the first 

 granules. 



The contents of one of the bottles was poured upon a filter ; 

 a perfectly clear liquid passed through, having a feeble yellowish 

 tint and a strong acid reaction. The substance on the filter con- 

 sisted almost wholly of the butter, mingled however with a small 

 quantity of a nitrogenous body like coagulated caseine, and 

 affording many of the reactions of that substance. It would, 

 however, be impossible to say that it was unaltered, as the reac- 

 tions which the coagulated forms of all the albuminous bodies 

 afford are so similar that it is always difficult, if not indeed im- 

 possible in the present state of chemistry, to determine which 

 of these bodies we may be dealing with. 



Part of the glycerides composing the butter had been decom- 

 posed and their acids set free. The granules which had been 



* Communicated by the Author. 



