PROTEINS OF THE MUSCLES. 569 



by saturating the filtrate with the salt. It is .similar to serglobulin, but coagu- 

 lates at 63 C. (HALLIBURTON). Myoalbumin, or muscle-albumin, seems to 

 be identical with seralbumin (seralbumin a, according to HALLIBURTON), and 

 probably originates only from the blood or the lymph. Proteoses and peptones 

 do not seem to exist in the fresh muscles. 



After the complete removal from the muscle of all protein bodies which are 

 soluble in water and ammonium chloride, an insoluble protein remains which 

 only swells in ammonium-chloride solution, and which forms with the other insoluble 

 constituents of the muscular fiber the " muscle-stroma" According to DANILEW- 

 SKY the amount of such stroma substance is connected with the muscle activity. 

 He maintains that the muscles contain a greater amount of this substance, com- 

 pared with the myosin present, when the muscles are quickly contracted and 

 relaxed, the correctness of which report has recently been disputed by SAXL.* 



According to J. HOLMGREN, 2 this stroma substance does not belong to either 

 the nucleoalbumin or the nucleoprotein group. It is not a glucoproteid, as it 

 does not yield a reducing substance when boiled with dilute mineral acids. It is 

 very similar to the coagulable proteins, and dissolves in dilute alkalies, forming 

 an albuminate. The elementary composition of this substance is almost the same 

 as that of myosin. There is no doubt that the insoluble substances, myofibrin 

 and myosin fibrin, which are formed, according to v. FURTH, in the coagulation of 

 the plasma, also occur among the stroma substances. When the muscles are 

 previously extracted with water, the stroma substances also contain a part of the 

 myosin hereby made insoluble. The observations of SAXL on rabbits' muscles 

 agree with this view that the fresh muscle after work contains 11.5-21.6 per cent 

 of the total protein in an insoluble form, while the muscle after rigor mortis con- 

 tains on the contrary 71.5-73.2 per cent. 



To the proteins insoluble in water, and neutral salts, belongs the 

 nucleoprotein detected by PEKELHARING, which occurs as traces and is 

 soluble in faintly alkaline water, and which probably originates from 

 the muscle nuclei. According to BOTTAZZI and DuccEScm 3 the heart 

 muscle is richer in nucleoprotein than the skeletal muscle. 



Muscle-syntonin, which may be obtained by extracting the muscles with 

 hydrochloric acid of 1 p.m., and which, according to K. MORNER. is less soluble 

 and has a greater aptitude to precipitate than other acid albumins, seems not 

 to occur preformed in the muscles. HEUBNER's 4 mytolin is modified muscle- 

 proteid, chiefly myosin, which has lost a part of its sulphur by the action of alkali. 



Proteins of the Muscle-plasma. As above stated, myosin was ordi- 

 narily considered as the coagulated modification of a soluble protein 

 existing in the muscle-plasma. As in blood-plasma there is present 

 a mother-substance of fibrin, fibrinogen, so also there exists in the 

 muscle-plasma a mother-substance of myosin, a soluble myosin or a 

 myosinogen. This body has not thus far been isolated with certainty. 



1 Hofmeister's Breitage, 9. 



2 See footnote 1, p. 566. 



3 Pekelharing, Zeitschr. f. physiol. Chem., 22; Bottazzi and Ducceschi, Centralbl. 

 f. Physiol., 12. 



4 Arch. f. exp. Pathol. u. Pharm., 53. 



