542 MUSCLES. 



goes into solution, and may be precipitated therefrom by carefully 

 acidifying. It separates from a dilute salt solution on dialysis. Mus- 

 culin readily passes into an insoluble modification which v. FURTH calls 

 myosin fibrin. Musculin is called myosin by v. FURTH, as he considers 

 it nothing but myosin. As musculin has a lower coagulation temper- 

 ature and has other precipitating properties for neutral salts than the 

 older substance called myosin, it is difficult to accept this view. 



Myoglobulin. After the separation of the musculin and the myosin from the 

 salt extract of the muscle by means of MgSO 4 , the myoglobulin may be precipitated 

 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 fibre the 

 '* muscle-stroma." According to DANILEWSKY the amount of such stroma 

 substance is connected with the muscle activity. He maintains that 

 the muscles contain a greater amount of this substance, compared with 

 the myosin present, when the muscles are quickly contracted and 

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



SAXL. 1 



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 coaguable proteins, 

 and dissolves in dilute alkalies, forming an albuminate. The elementary 

 composition of this substance is nearly 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 contains 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 



1 Hofmeister's Beitrage, 9. 2 See footnote 1, p. 539. 



