METABOLISM IN MUSCLE. 549 



extracted from muscle-juice by means of a 5 to 10 per cent, solution of ammon- 

 ium chlorid. Myosin belongs to the globulins; Halliburton has prepared it also 

 from the muscles of warm-blooded animals. It is precipitated from its solutions 

 by saturation with sodium chlorid or magnesium sulphate. When dissolved 

 in a 10 per cent, solution of sodium chlorid, it is coagulated by heat. It is 

 dissolved by 2 per cent, hydrochloric acid, with the formation of acid-albumin 

 (syntonin), and by alkalies or alkaline carbonates, with the formation of alkali- 

 albuminate. Like fibrin, myosin actively decomposes hydrogen dioxid. A. 

 Danilewsky has succeeded in reconverting syntonin in part into myosin. Myosin 

 is not present in unstriated muscles. 



Muscle-serum contains further small amounts of myoalbumin (C 114 - 

 H 17 4N 30 SO 30 ), which is coagulable at 73 C., but is not precipitated by sat- 

 uration of the serum with magnesium sulphate ; also my o globulin, which is 

 precipitated by this last procedure, and is coagulable at 63 C.; and a 

 little nucleoalbumin. 



Halliburton distinguishes the following proteids in muscle: (i) Paramyosino- 

 gen, or musculin, a globulin-like body, forming 20 per cent, of the total proteids, 

 and coagulating at 47 C. (2) Myosinogen, forming 77 per cent, of the total 

 proteids, coagulating at 55. Both of these bodies are coagulable spontaneously, 

 forming myosin. (3) According to v. Furth myosinogen gives rise to myogen- 

 fibrin, which is soluble, is coagulable at 35, and, like paramyosinogen, is readily 

 transformed into a fibrin-like modification that is dissolved with difficulty. Cer- 

 tain salts or organic substances (caffein, veratrin) accelerate this process, while 

 it is inhibited by blood-serum, and also by egg-albumin. (4) Myoalbumin, which is 

 similar to serum-albumin. The coloring-matter of muscle (myohematin) appears 

 to be different from hemoglobin. The absorption-bands are situated somewhat 

 nearer to the red end of the spectrum. According to Levy, myohematin is identical 

 with hemochromogen. There is an oxidized and a reduced myohematin (by am- 

 monium sulphid). The muscle-nuclei yield some nuclein. The sarcolemma con- 

 tains a substance resembling keratin. Several ferments are present in traces: 

 pepsin, diastatic, lactic-acid (?), glycolytic, and coagulating (fibrin-) ferments. 

 Proteic acid is a proteid substance in the flesh of fish. 



The other chemical constituents of muscle have already been mentioned in 

 the consideration of meat (p. 423). It will suffice to add a little more here, (i) 

 In addition to volatile fatty acids (formic, acetic, and butyric acids), two isomeric 

 lactic acids are found in muscle having an acid reaction : (a) Ethylidene-lactic acid 

 in the modification of dextrorotatory paralactic or sarcolactic acid, (b) Ethylene- 

 lactic acid in small amount, which Maly also observed develop as an occasional 

 fermentation-product of carbohydrates (glycogen, etc.). The formation of lactic 

 acid during the rigidity of death is discussed on p. 552. Acid potassium phosphate 

 also contributes to the acid reaction. (2) Glycogen is found to the amount of 

 i per cent, after an abundant meat-diet, and of 0.5 per cent, during fasting. 

 During digestion it is stored up in the muscles, as well as in the liver, but it dis- 

 appears in the state of hunger. It is formed in the muscles themselves, probably 

 from albuminates. (3) Dextrose, 0.02 per cent. (4) Of gases, there are present 

 carbon dioxid (from 15 to 18 vol. per cent., partly absorbed, partly in chemical 

 combination, the latter probably being formed as a result of decomposition), 

 some absorbed nitrogen; but no oxygen, although muscle continually absorbs 

 oxygen from the blood. The muscles contain a substance that yields carbon 

 dioxid on decomposition; exercise consumes this substance, so that muscles that 

 are greatly fatigued are capable of generating less carbon dioxid. 



METABOLISM IN MUSCLE. THE SOURCE OF MUSCULAR 



ENERGY. 



The resting muscle continuously abstracts oxygen from, and returns 

 carbon dioxid to, the capillary blood passing through it. Nevertheless, 

 the muscle excretes less carbon dioxid than corresponds to the amount 

 of oxygen it absorbs. Excised muscles deprived of blood exhibit an 

 analogous but diminished interchange of gases. Further, as such muscles 



