206 Mr. W. K. Sullivan on the nature of Lactic Fermentation. 



gulum, he found that a similar body remained in solution, and 

 could only be thrown down by boiling the hydrochloric acid 

 solution. 



At present there is no satisfactory mode of accounting for the 

 formation of caseine in the mammary glands. According to the 

 observations of Lassaigne, made a considerable time ago*, the 

 milk is alkaline, and highly charged with albumen forty days 

 before calving, and only ten days before that period does the 

 sugar of milk appear. Some writers also state that albumen 

 sometimes exists in milk during inflammation of the mammary 

 glands. Among others, Moleschott found it in cow's milk. It 

 may, however, be observed that Scherer prepared from normal 

 milk a caseine coagulable by heat, and that where coagulation 

 alone is depended upon, erroneous results may be obtained. 

 Lehmann has drawn attention to this source of doubt ; but, on 

 the other hand, may it not be equally well asserted that the 

 coagulable caseine of Scherer was no longer true caseine, but 

 albumen ? A phsenomenon the reverse of this has, indeed, been 

 observed in the case of the albumen of serum by Hofmann. 

 When serum is digested at the temperature of 31° to 44° with 

 a piece of rennet, the liquor becomes troubled in the course of 

 about twenty-four hours, and little by little it becomes filled with 

 a flocculent precipitate. The filtered liquor is perfectly neutral, 

 and does not coagidate by boiling, but forms a pellicle on evapo- 

 ration exactly like caseine. 



An explanation of the phsenomena of the change of albumen 

 into caseine in the animal body, and the reabsorption of the 

 caseine into the blood, would be of great interest ; much light 

 may be thrown upon these questions by a complete series of ob- 

 servations carried ou.t from the same point of view as those of 

 Lassaigne, above alluded to. 



In describing the changes which the caseine of the milk un- 

 derwent as a conversion into albumen, I have naturally assumed 

 that the distinctive reactions between both those bodies, usually 

 relied upon by chemists and physiologists, are such as fulfil 

 the conditions which science demands. It is right, however, to 

 state that, as distinctive tests, they do not, in my opinion, pos- 

 sess the value assigned to them. I believe, and I am sure all 

 who have worked upon the albuminous bodies will agree with 

 me, that no known reaction can be relied upon as a satisfactory 

 distinctive test between two such closely-allied substances as 

 albumen and caseine. But even if we admit that the reactions 

 which I have described do not prove absolutely the conversion 

 of caseine into albumen, assumed to have taken place, the change 



* " Examen physique et cbimique du lait de Vacbe avant et ai)res le 

 part," Ann. de Chim. et de Phys, 1832, vol.xlix. p. 31. 



