414 THE GLANDULAR ORGANS. 



cows' milk, and is manifestly closely related to the common scrum- 

 albumin of the blood-plasma. Its specific rotation, however, is 

 markedly less, viz., 37 degrees, as compared with 62.6 to 64.6 

 degrees. Its composition according to Sebclicn is C, 52.19 per cent. ; 

 H, 7.18; N. 15.77; S, 1.73; and O, 23.13; while that of serum- 

 albiimm is given as 0,52.25-53.06 per cent.; H, 6.65-6.85; N, 

 15.88-16.04; S, 1.8-2.25; and O, 22.25-22.97 (Hammarsten). 



LACTOGLOBULIN. The lactoglobulin which has been isolated 

 from cows 7 milk seems to be identical with the scrum-globulin 

 of the blood. It requires no further description. 



That still other albuminous substances may occur in the milk is 

 possible; but if so, they are present only in traces and have not as 

 yet been identified. Albunioses and peptones are not found in 

 fresh milk. According to Siegfried, a phosphor-earn ic acid can be 

 isolated from milk after removal of the casein and the coagulable 

 albumins ; this, however, is supposedly not identical with that found 

 in muscle-plasma. 



Origin of the Albumins. Casein, as has been stated, is a specific 

 product of the activity of the mammary glands, and is probably 

 formed from the complex nucleo-glucoproteid which occurs in the 

 functionally active organ. As this is not found in the milk, we may 

 conclude that after its formation it is decomposed and probably 

 yields casein, on the one hand ; while its reducing radicle may be 

 concerned in the production of lactose. 



Of the origin of lactoglobulin and lactalbumin, nothing is known; 

 but, as I have said, the former is probably identical with the serum- 

 globulin of the blood, while in the case of the latter we may 

 imagine that it has originated through a peculiar transformation of 

 the serum-albumin. 



Isolation of the Albumins of the Milk. ISOLATION OF CASEIN. 

 The milk is diluted with four times its volume of water and acidi- 

 fied with acetic acid to the extent of 0.75-1.0 pro mille. On stand- 

 ing, the casein separates out and is filtered off. It is purified by 

 repeated solution in water with the aid of a little caustic alkali, 

 filtration, and reprecipitation with acetic acid. It is then washed 

 with water and freed from traces of fat by means of ether-alcohol. 

 The greater portion of the fat remains on the first filter. 



ISOLATION OF LACTOGLOBULIN. The milk is saturated with 

 common salt in substance, which precipitates the lime-casein to- 

 gether with a small portion of the globulin. If then the neutral 

 filtrate is saturated with magnesium sulphate at 30 C.,the remain- 

 ing portion of the lactoglobulin is obtained. This is purified as 

 described on page 314. 



ISOLATION OF LA<TALI',U.MIN. Tin; lime-caseVn and globulin are 

 first precipitated by salting with magnesium sulphate in substance at 

 30 C., and are filtered off. In the filtrate the lactalbumiu can 

 then be demonstrated by acidifying with acetic acid to the extent 

 of a little less than 1 per cent., or by salting with ammonium sul- 



