166 EXPERIMENT STATION RECORD. 



milk and the means of treating cows' milk so as to nuike it resemble 

 human milk more closely as a food. These investigations are the sub- 

 ject of the present paper. 



Lehmann's method of determining casein was by means of nnglazed 

 porcelain plates, and was briefly as follows: The plate was wet with 

 water and then 10 cc. of a mixture of equal parts of milk and water 

 l)laced in the center. The serum separated in about an lionr and a half, 

 when the mixture of fat and casein was removed with a si)atula and 

 finally by setting the plate in water to free the last traces. This was 

 placed on a weighed filter and washed with ether, the last traces of fat 

 being removed by rubbing the casein in a glass mortar and then wash- 

 ing Avith ether. The casein was dried and then incinerated for ash. 

 The determinations of fat and casein by this method are said to be 

 very accurate. With practice G determinations can be made in a day. 

 The casein is obtained in a natural, undecomi^osed condition, and is 

 termed by Lehmaun "genuine" casein for this reason. 



As a result of numerous determinaticms it was found that the "gen- 

 uine" (^asein of cows' milk contained, on an average, 7.2 per cent of ash, 

 and that the ash contained : 



CaO, 49.8 per cent, eqnivaleut to .3.20 per cent in water-free casein. 

 MgO, 2.1 per cent, equivalent to 0.10 per cent in water-free ca.sein. 

 KcO, 0.9 per cent, equivalent to 0.06 per cent in water-free casein. 

 Na^O, 0.4 per ci-nt, equivalent to 0.03 per cent in water- free casein. 

 P-jOs, 45.0 per cent, equivalent to 2.92 per cent in water-free casein. 

 .SO:,, 1.2 per cent, equivalent to 0.08 per cent in water-free casein. 



The indications were that the phosphorus in casein is all in the form 

 of an ester-like compound derived from phosphoric acid, and tliat 

 casein is to be regarded as a double compound of casein.-calcium with 

 calcium i)hosphate. From 1.45 to 1.75 per cent of CaO was found to be 

 combined directly with the casein. The relation of casein-calcium to 

 calcium phosphate in one series of experiments agreed with the formula 

 Ca:)(IH)4).2.Ca-casein; but in other cases the proportion of calcium 

 phos])hate was too small for this. 



The average elementary composition of "genuine" casein was found 

 to be: Ash, ().47 per cent (mostly as calcium phosphate); carbon, 50.S(5; 

 hydrogen, 6.72; nitrogen, 14.03; phosphorus, 0.81, and sulphur, 0.72; or 

 calculated to ash -free casein, carbon, 54 per cent; hydrogen, 7.04; nitro- 

 gen, 15.0; phosphcn'us, 0.847; and sulphur 0.771. 



Casein from cows' milk and from human milk differed widely in 

 respect to sulphur and calcium phosphate, "showing that they are 

 undoubtedly two different caseins." While "genuine" casein from cows' 

 milk contained 0.723 per cent of sulphur and 0.6 per cent of calcium 

 phosphate, "genuine" casein from human milk contained 1.09 per cent 

 of sulphur but only 3.2 per cent of calcium phosphate. 



The average com])osition given by Lehmann for cows' milk and 

 human milk is as follows : 



