652 MILK. 



clems diminishes as the pepsin-hydrochloric acid increases. In the 

 presence of 500 grams of pepsin-hydrochloric acid to I gram of casein, 

 SALKOWSKI digested the latter completely without obtaining any 

 pseudonuclein. 



In peptic as well as tryptic digestion a part of the organic phosphorus 

 is split off as orthophosphoric acid, the quantity increasing as the diges- 

 tion progresses. Another part of the phosphorus is retained in organic 

 combination in the proteoses as well as in the true peptones (SALKOWSKI, 

 BIFFI, ALEXANDER, ADERS-PLIMMER and BAYLISS l ). 



From the products of peptic digestion of casein, after the separation of the 

 pseudonuclein, SALKOWSKI 2 has isolated an acid rich in phosphorus. He con- 

 siders this a paranudeic acid. This acid which gives the biuret test and a 

 faint xanthoproteic reaction, contains 4.05-4.31 per cent phosphorus. A still 

 richer product in phosphorus, with 6.9 per cent P, has been isolated by REH 

 from the peptic digestive products of casein. He calls this body polypeptid 

 phosphoric acid. This product, which also gives the above-mentioned protein re- 

 actions, and is not comparable with the nucleic acids, is characterized by a remark- 

 ably high content of ami no-nitrogen, namely. 23.8 per cent. Among the products 

 obtained by REH, DIETRICH 3 found a mixture of at least four different lime-salts 

 of a peptone character, and which he considers as polypeptide-like combination 

 with P 2 O 5 , caseonphosphoric acids. The amount of phosphorus was, respectively, 

 10.0, 4.1, 3.84 and 3.88 per cent. 



Casein may be prepared in the following way: The milk is diluted 

 with 4 vols. of water and the mixture treated with acetic acid to 0.75- 

 1 p. m. Casein thus obtained is purified by repeatedly dissolving in water 

 with the aid of the smallest quantity of alkali possible, by filtering and 

 reprecipitating with acetic acid and thoroughly washing with water. 

 Most of the milk-fat is retained by the filter on the first filtration, and the 

 casein contaminated with traces of fat is purified by treating with alcohol 

 and ether. 



Lactoglobulin was obtained by SEBELIEN from cow's milk by saturating 

 it with NaCl in substance (which precipitated the casein) and saturating 

 the filtrate with magnesium sulphate. As far as it has been investigated 

 it had the properties of serglobulin; the globulin isolated by TiEMANN 4 

 from colostrum had, nevertheless, a markedly low content of carbon, 

 namely, 49.83 per cent. 



Lactalbumin was first prepared in a pure state from milk by SEBELIEN. 

 He gives its composition as, C 52.19, H 7.18, N 15.77, S 1.73, O 23.13 

 per cent. Lactalbumin has the properties of the albumins, and WICH- 



^alkowski, 1. c.; Biffi, Virchow's Arch., 152; Alexander, Zeitschr. f. physiol. 

 Chem., 25; Plimmer and Bayliss, Journ. of Physiol., 33; See also Kiittner, Pfliiger'a 

 Arch. 129. 



2 Zeitschr. f. physiol. Chem., 32. 



3 Reh. Hofmeister's Beitrage 11; Dietrich, Bioch. Zeitschr. 22. 



4 Zeitschr. f. physiol. Chem., 25. 



