io 4 THE CHEMISTRY OF THE TISSUES AND ORGANS. 



has been further confirmed by Frankel, 1 who finds that pure amplio- 

 peptone is also sulphur-free. 



Phosphocarnic acid has a complicated molecule ; it yields on 

 decomposition carnic acid, carbonic anhydride, succinic acid, sarcolactic 

 acid, and a strongly reducing carbohydrate. Siegfried compares it to 

 nuclein; but nucleins yield proteid on decomposition; phosphocarnic 

 acid yields carnic acid (antipeptoiie) instead; he suggests the term 

 nucleon for it. The percentage of this substance in human muscle is 

 0'1-0'2. In new-born children the muscles contain less (0 to 0'06 per 

 cent. 2 



A phosphocarnic acid is also found in milk, but differs from that in 

 muscle by yielding fermentation lactic acid instead of sarcolactic acid 

 on decomposition. 3 



Kriiger* has found that on hydrolysis and simultaneous oxidation by 

 means of ferric chloride, phosphocarnic acid gives off carbonic anhydride ; 

 no other substance in muscle extracts does this. He therefore looks 

 upon it as the material in muscle which during muscular activity gives 

 off carbonic anhydride without using up oxygen. This is a conclusion 

 that requires serious consideration and renewed research before it can 

 be accepted, but it is another indication of the importance of Siegfried's 

 work. 



We now pass to the non-nitrogenous extractives : 



Glycogcn. This substance may be extracted from muscle by hot 

 water 5 ; or by dilute potash 6 ; the latter reagent HVrc.ts a, much more, 

 thorough extraction. Cramer, 7 using Kiilz's method, found that different 

 groups of muscles contain varying amounts of glycogen, but that corre- 

 sponding muscles of the two sides of the body contain the same amount. 

 In the heart, glycogen is unequally distributed in the different regions 

 (Cramer). The average percentage of glycogen in fresh heart muscle 

 is, however, about the same as in voluntary muscle, though it dis- 

 appears after death (being converted into sugar as in the liver) more 

 rapidly than in skeletal muscle. 8 Glycogen also occurs in other 

 involuntary muscles. 9 



The glycogen in muscle during life varies in quantity. The following 

 are the principal causes of variation : 



1. Starvation. The muscle glycogen disappears during inanition, but 

 much more slowly than the hepatic glycogen. 10 Luchsinger 11 stated 

 that the glycogen of the heart muscle disappears still less quickly, but 

 Aldehoff (using Kiilz's method) could not confirm this. 



1 Loc. cii. 



2 M. Miiller, Ztschr. f. physiol. Chem., Strassburg, 1897, Bd. xxii. S. 561. 



:; K. Wittmaack (ibid., S. 567) gives the percentage of nucleon in human milk as 0'124 ; 

 in cows' milk, 0'056, and in goats' milk, O'll. Blumenthal (Vircliow's Archiv, Bd. cxlvi. 

 S. 65) gives the percentage in cows' milk as 0'05. 



4 Ztschr. f. physiol. Chem., Strassburg, 1896. Bd. xxii. S. 95. 



5 Briicke, Sitzungsb. d. k. Akad. d. Wissensch., Wicn, 1871, Bd. Ixiii. Abtli. 2, S. 214 ; 

 Nasse, Arch. f. d. ges. Physiol., Bonn, Bd. ii. S. 97. 



6 Abeles, Med. Jahrb., Wien, 1877, S. 551 : Ktilz, Ztschr. f. Bid., Mlinchcn, Bd. xxii. 

 S. 161. See also Schmelz, ibid., Bd. xxv. S. 180. 



7 Ibid., Bd. xxiv. S. 67. 



8 Boruttau, Ztschr. f. physiol Chem., Strassburg, Bd. xviii. S. 513. 



9 In the stomach, Briicke, loc. cit. ; in the plain muscles of gastropods, Chittenden, 

 Ann. d. Chem., Leipzig, Bd. clxxviii. S. 266 ; Bizio, Atti. r. 1st. Veneto di sc., lett. et arti, 

 1866, Se>. 3, tome i. 



10 Weiss, Sitzungsb. d. k. Akad. d. Wisscnsch., Wien, Bd. Ixiv. ; Aldehoff, Ztschr. f. 

 J3ioL, Miinchen, Bd. xxv. S. 137. 



11 Dissertation, Zurich, 1875. 



