Primary Cleavage Products. 365 
content of sulphur into a body richer in sulphur, is hard to see. 
Much more plausible is it, as suggested by Hammarsten, that in 
these two bodies we have to deal with the same substance, in the 
one case united with calcium phosphate, and in the other uncom- 
bined with this salt; or in other words that the so-called protalbin 
body in the absence of calcium phosphate is soluble in boiling 50 per 
cent. alcohol, while in the presence of that salt it is insoluble. 
This view being correct, and Hammarsten’s observations would 
tend to show that it is, it is obvious that the caseoprotalbin of Dan- 
ilewsky is simply a portion of the casein, which, owing to lack 
of a sufficient amount of calcium phosphate, passes into solution on 
being boiled with dilute alcohol; while caseoalbumin, on the other 
hand, is likewise a portion of the casein, insoluble on account of.the 
presence of calcium phosphate; changed, however, more or less by 
action of the boiling alcohol. Further, the reason why casein 
precipitated several times by acetic acid does not contain as much 
calcium phosphate as when precipitated by hydrochloric acid, and 
thus reacts differently with alcohol, depends on the far greater insol- 
ubility of freshly precipitated casein in excess of acetic acid than in 
hydrochloric acid. In the precipitation of casein with hydrochloric 
acid only the slightest excess of acid can be added, on account of the 
ready solubility of the precipitate in this dilute acid. With acetic 
acid, however, a moderate excess can be added without solution of 
the precipitate, and thus in the latter case, a larger proportion of 
mineral salts are removed at each re-precipitation. 
Danilewsky and Radenhausen have further called attention to the 
fact that casein precipitated with hydrochloric acid yields a larger 
amount of alkaline sulphide than when precipitated by acetic acid. 
This statement, Hammarsten has several times been able to verify, 
but the latter investigator seeks an explanation for this fact in the 
occasional: presence of a second albuminous body, richer in sulphur, 
presumably serum-globulin, precipitable like casein by acids. Serum- 
globulin too, is readily soluble in excess of acid, even more so 
than casein, and hence by the acetic acid method of precipitation, 
which allows a far greater excess of acid, the casein would be much 
less liable to contamination by this hypothetical globulin than by the 
hydrochloric acid method. In this connection it may be well to 
notice that Musso and Menozzi* claim the presence in milk of a 
peculiar albuminous body containing 53°74 per cent. C, 15°52 per 
* Studien iiber das Eiweiss der Milch. Jahresbericht fiir Thierchemie, 1878, p. 139. 
