378 



PROTEIN-COMPOUNDS. 



resembles album en, although it yields a larger amount of acetic 

 acid. (Guckelberger.*) 



Simon has directed attention to certain differences presented by 

 casein from women's milky cows' milk, and the milk of the bitch. 

 Casein from women's milk is white or yellowish, friable, becomes 

 moist on exposure to the air, is insoluble in alcohol, but dissolves 

 in water, forming a turbid, frothy fluid, from which it is completely 

 thrown down by tannic acid, acetate of lead, and corrosive subli- 

 mate, and imperfectly precipitated by acetic acid and alum. 

 Casein from cows' milk is not so freely soluble in water, and, when 

 dry, is tough and horny ; while that from the milk of the bitch is 

 not tough and horny, and is difficult of solution in water. Dumas 

 has, however, ascertained that the composition of these three kinds 

 of casein is perfectly identical. There is much here that requires 

 explanation. Simon's observations are certainly correct ; and 

 can not only confirm his statements from my own experience, but 

 also those of Elsasser, according to which the cheesy coagulum of 

 women's milk is always loose and jelly-like in its texture, while 

 that of cows' milk is very firm and clotty. These differences may, 

 however, be found to depend on many external relations, on the 

 admixture of various substances, &c. Thus, for instance, I believe 

 that the jelly-like coagula of women's milk are more dependent on 

 the alkaline state of the fluid than on any peculiarity in the casein; 

 at all events, I have found that women's milk, when acid, yields a 

 much thicker coagulum than when alkaline, and cows' milk, when 

 alkaline, a much looser coagulum than when acid ; facts of the 

 highest interest and value in relation to dietetics. 



Composition. Casein, like albumen, has very often been ana- 

 lysed, but all these analyses have led to no perfectly certain empi- 

 rical formula, and far less to a rational one. We give as examples, 

 analyses by 



Carbon .... 

 Hydrogen 

 Nitrogen 

 Oxygen .... 

 Sulphur .... 



Mulder.t 



53-83 



7'15 



15-65 



23-37 



100-00 



Scherer.J 



54-665 



7'465 



15-724 



22-146 

 100-000 



and Dumas. 

 53-7 

 7*2 

 16-6 



22-5 



lOO'O 



* Ann. d. Ch. u. Pharm. Bd. 64, S. 39-100. 

 t Bullet, de Nrferl. 1839, p. 10. 

 Ann. d. Ch. u. Pharm. Bd. 40, S. 40. 

 Compt. raid. T. 21, p. 715. 



