ix THE MUSCLE-ALBUMINS 393 



and Siegfried's l observation as to the occurrence of carnic- or sarctic- 

 acid in muscle must be mentioned, although it is very uncertain as to 

 whether this acid occurs normally in muscle. 2 The observations of 

 Mays and Siegfried have, perhaps, some bearing on those of Pekel- 

 haring 3 and Kossel, 3 who obtained a nucleo-proteid from the nuclei of 

 muscle. Holmgren 4 has finally described a very insoluble albumin, 

 which can only be extracted as an alkali-albuminate, and of which it 

 is difficult to say whether it is a coagulated albumin or whether it is 

 an albuminoid, forming a part of the muscle -stroma. It will be dis- 

 cussed later amongst the albuminoids. 



Whether albuminous substances resembling paramyosinogen (v. 

 Fiirth's myosin) occur also in other organs is a difficult question. All 

 tissues undergo in a certain sense rigor mortis, and therefore it is 

 legitimate to say that substances coagulating spontaneously are present 

 in every cell. Reinke and Rodewald 5 found such a bodyjn the proto- 

 plasm of jEthalium septicum. Plosz 6 obtained from the liver an 

 albumin having the coagulation-temperature of myosin (47) ; Lilien- 

 feld T a similar compound in the leucocytes of the thymus gland ; 

 Chittenden 8 obtained paramyosinogen from the retina ; and Halli- 

 burton 9 isolated from many organs rich in cells (spleen, thyroid, etc.) 

 albumins having the coagulation -temperature of myosin; he failed, 

 however, in finding this albumin in the brain and in red corpuscles. 

 It is also possible to extract from the pancreas an albumin which co- 

 agulates spontaneously at body-temperature, and which also resembles 

 paramyosinogen in other respects; it possesses a coagulation -tem- 

 perature of 50 or somewhat less ; its salting-out limits for ammonium 

 sulphate lie between 1 *5 and 3, or as low as in the case of fibrinogen and 

 paramyosinogen. Spontaneously coagulable albumins are also found 

 in mucous membranes. For all these reasons one may regard myosin 

 as forming an integral part of every kind of protoplasmic molecule. 



The nucleo-proteids are most abundant in nonstriped muscle, then 



. l M. Siegfried, Arch. f. Anat. u. PhysioL, Physiol. Abteil. 1894, p. 401 ; Zeitschr. 

 f. physiol. Chem. 21. 360 (1895) ; 28. 524 (1899) ; J. Macleod, ibid. 28. 535 (1899). 



- See on this point Halliburton, Biochemistry of Muscle and Nerve (1904), p. 46. 



:J C. A. Pekelharing, Zeitschr. f. physiol. Chem. 22. 245 (1896) ; A. Kossel, ibid. 7. 

 7 (1882). 



4 J. F. v. Holmgren, from the Swedish original by Hammarsten in Holy's Jahresber. 

 f. Tierchemie, 23. 360 (1893). 



5 J. Reinke and H. Rodewald, Botanikerztg. 38. (1880). 



6 P. Plosz, Pflugers Arch. 7. 371 (1873). 



7 L. Lilienfeld, Zeitschr. f. physiol. Chem. 18. 473 (1893). 



8 R. H. Chittenden, " Histoeheniie des Sehepithels," Untersuchungen aus dem Heidel- 

 berger physiologischen Institute, 2. 438 (1879). 9 See p. 406. 



