546 MUSCLES. 



hypoxanthine. In the embryonic ox-muscles, KossEL 1 found more 

 guanine than hypoxanthine. The purine bases are produced in the 

 muscles themselves, and their production, which also takes place while 

 at rest, is greatly increased during work (BURIAN 2 ) . 



Among the apparently habitually occurring nitrogenous extractives, 

 we should also mention phosphocarnic acid as well as inosinic acid, which 

 is perhaps allied to it, carnosine, carnitine, and perhaps also other bodies 

 which have recently been found in meat extract and which will be men- 

 tioned later. 



Among the extractive substances is also found the acid noticed by LIMPRICHT 

 in the flesh of certain cyprinidea, namely, the nitrogenized protic acid, while the 

 isocreatinine found by J. THESEN in fish-flesh is nothing but impure creatinine, 

 according to POULSSON, SCHMIDT and KoRNDORFER. 3 Uric acid, urea, taurine, 

 and leucine are found as traces in the muscles, in certain cases only in a few species 

 of animals. In regard to the amounts of these different extractives in the muscles, 

 KRUKENBERG and WAGNER 4 have shown that they vary greatly in different 

 animals. A large quantity of urea is found in the muscles of the shark and ray; 

 uric acid is found in alligators ; taurine in cephalopoda ; glycocoll in gasteropoda, 

 and creatinine especially in fishes. The reports are very contradictory in regard 

 to the occurrence of urea in the muscles of higher animals. According to the 

 investigations of KAUFMANN and SCHONDORFF, confirmed by BRUNTON-BLAIKIE, S 

 urea is a regular constituent of the muscles, although M. NENCKI and KOWARSKI 

 dispute this. 



The purine bases, with the exception of carnine, have been treated 

 on pages 184-188, and therefore among the extractive bodies we will 

 first consider the creatine. 



/NH 2 

 Creatine, C4H 9 N 3 O2, C^=NH , or methyl-guanidine- 



\N(CH 3 ).CH 2 COOH 



acetic acid, occurs in the muscles of vertebrate animals in variable amounts, 

 1.4-5 p. m., in different species; the largest quantity is found in birds. 

 It is also found in the brain, blood, transudates, amniotic fluid, and some- 

 times also in the urine. Creatine may be prepared synthetically from 

 cyanamide and sarcosine (methylglycocoll) . On boiling with baryta- 

 water it decomposes, with the addition of water, and yields urea, sarcosine, 

 and certain other products. Because of this behavior several investiga- 



1 Burian and Hall, Zeitschr. f. physiol. Chem., 38; Kossel, ibid., 8, 408. 



2 Ibid., 43. 



3 See Limpricht, Annal. d. Chem. u. Pharm., 127, and Thesen, Zeitschr. f. physiol. 

 Chem., 24; Poulsson, Arch. f. exp. Path. u. Pharm., 51; Schmidt and Korndorfer, 

 ibid., 51. 



4 Zeitschr. f. Biologic, 21; see also M. Henze, Zeitschr. f. physiol. Chem., 43; 

 Mendel, Hofmeister's Beitrage, 5; Kelly, ibid., 5. 



5 Kaufmann, Arch, de Physiol. (5), 6; Schondorff, Pfliiger's Arch., 62; Nencki 

 and Kowarski, Arch. f. exp. Path. u. Pharm., 36; Brunton-Blaikie, Journ. of Physiol., 

 23, Supplement. 



