396 CHEMISTRY OF THE PROTEIDS CHAP. 



digestion, while according to Biffi l it is separated off by tryptic 

 digestion. 



The precipitation of paranucleic acid by peptic digestion is never 

 complete, and this explains the statements made by Alexander 2 and 

 others regarding the phosphorus-content of casein-albumoses. Sal- 

 kowski has precipitated the paranucleic acid of casein by means of 

 ferri-ammonium sulphate, and has then decomposed the precipitate 

 with sodium-hydrate solution. Levene and Alsberg 3 dissolved the 

 nucleo-albumin with ammonia, acidified and then precipitated the 

 albumin-moiety with picric acid and the paranucleic acid with 

 alcohol 



Paranucleic acid precipitates albumin, 4 and is precipitated by 

 the salts of the heavy metals and by some of the alkaloidal reagents. 

 In its pure, non-albuminous state paranucleic acid is not known, and 

 its dissociation-products are also unknown. 



Attempts to make artificial nucleo-albumins by combining thyminic 

 acid or other preparations with albumins have given negative results. 5 

 The pseudo-nucleins formed in this way are readily dissolved by 

 trypsin, easily absorbed by the intestine, and excreted as phosphoric 

 acid by the kidneys. 6 



The sulphur -component has been studied by v. Moraczewski, 7 

 by digesting different strengths of casein-solutions for different lengths 

 of time with different amounts of pepsin and hydrochloric acid. He 

 found that the sulphur-content of the paranuclein varies but little 

 under different conditions. There is thus a marked difference in the 

 behaviour of the sulphur and the phosphorus. Whether the para- 

 nuclein percentage of the original casein was 2 or was 1 2 per cent, the 

 sulphur-content varied between 0*32 and 0'40 per cent of sulphur. 

 During digestion a part of the sulphur volatilises, and the more 

 intense the digestion, the greater also is the amount of the sulphur 

 which is lost. 



1 U. Biffi, Virckow's Archiv, 152. 130 (1888). 



2 F. Alexander, ibid. 25. 411 (1898). 



3 P. A. Levene and C. Alsberg, ibid. 31. 543 (1900). 



4 E. Salkowski, ZentrftlU. /. d. med. Wissensch. 1893, Nos. 23 and 28 ; Pjlugers 

 Arch.f. d. ges. Physiol. 63. 401 (1896) ; Zeitschr. /. physiol. Chem. 27- 297 (1899) ; 

 E. Salkowski and M. Hahn, Pflilger's Archiv f. d. ges. Physiol. 59. 225 (1895) ; 

 E. Salkowski, Zeitschr. f. physiol. Chem. 32. 245 (1901) ; compare also W. v. 

 Moraczewski, ibid. 20. 28 (1894) ; T. H. Milroy, Zeitschr. f. physiol. Chem. 22. 307 

 <1896). 



5 T. Milroy, ibid. 22. 307 (1896). 



6 W. Sandmeyer, ibid. 21. 87 (1895) ; J. Sebelieu, ibid. 20. 443 (1895). 



7 W. v. Moraczewski, Hofraeisters Beitr&ge, 5. 489 (1904). 



