86 PHYSIOLOGY OF MUSCLE AND NERVE 



them to a pressure of from 250-300 atmospheres. About 60 per cent, of the weight 

 of the muscle is then obtained as plasma. 



The Proteins of the Plasma. Halliburton, 1 has shown that muscle-plasma 

 contains two coagulable proteins, namely myosin and myogen which upon coagu- 

 lation are transformed into myosinfibrin and myogenfibrin. But this transfer 

 does not seem to be a direct one, because, in the case of myogen, v. Fiirth has found 

 an intermediary product which he has called soluble myogenfibrin. This author 

 also calls attention to the fact that the coagulation of muscle-plasma is not strictly 

 comparable to the coagulation of blood, as has been held by Kiihne and Halli- 

 burton, because the clot is floccular and forms as a rule very slowly. Furthermore, 

 while fresh muscle-plasma is neutral or slightly alkaline in reaction, it becomes 

 distinctly acid after coagulation has set in. This acidity is due to the formation 

 of sarcolactic acid. The serum formed in the course of this process, contains the 

 soluble constituents of muscle. 



The Proteins of the Stroma. The residue left over after the plasma has been 

 squeezed out, consists chiefly of connective tissue, sarcolemma and nuclei. By 

 preventing as much as possible the occurrence of rigor in the excised muscles, Saxl 2 

 has found that only a small portion of their total mass consists of stroma. He also 

 states that the plasma proteins in skeletal muscle amount to seven-eighths of the 

 total protein content, while their relationship in cardiac muscle 3 is as ^ : % and 

 in smooth muscle as 3^ :%. The stroma contains phosphorus which is held 

 in the nucleoprotein. It also embraces phospholipins in combination with the 

 proteins. 



Lipins of Muscle. The fat of muscle is contained chiefly in the connective 

 tissue between its different bundles, but a certain amount of it is also held in the 

 cells themselves. On analysis the former in all probability gives rise to neutral 

 fat, while the latter yields cholesterol and phospholipins. The proportion of these 

 bodies differs greatly in different types of muscle tissue. In skeletal muscle, they 

 may amount to as much as 30 per cent., and in cardiac muscle to as much as 60 

 or 70 per cent, of the total lipins. 4 Cardiac tissue is characterized by a large per- 

 centage of cuorin which is a monoamidodiphosphatide. 



Carbohydrates of Muscle. 5 The presence of glycogen in muscle tissue was 

 recognized soon after the discovery of this substance by Claude Bernard. It may 

 be present in considerable amounts, namely 1.0 per cent, in the muscles of the cat, 

 0.4-0.7 per cent, in those of man, and as much as 3.7 per cent, in those of the dog. 

 It seems to be derived from the sugar of the blood, muscle tissue possessing the 

 power of converting the monosaccharide dextrose by dehydration and condensa- 

 tion into the polysaccharide glycogen. The following formula may serve to illus- 

 trate this reaction;. 



N(C 6 H 12 O 6 ) - N(H 2 O) = (C 6 H 10 5 )N 



Glycogen is stored in the muscle tissue and forms an important nutritive material. 

 For this reason, it must be a constant constituent of all well-nourished resting 

 muscles. 



Inorganic Constituents. Muscle tissue contains a number of salts such as the 

 chlorides, sulphates and phosphates of sodium, potassium, calcium, magnesium 

 and iron, but its chief characteristic is its large content in potassium and phos- 

 phoric acid. 6 The total amount of phosphorus is 0.2 per cent., it being present 

 chiefly in an inorganic form. Ox muscle, for example, contains 81 per cent, of 

 inorganic and 19 per cent, of organic phosphorus, while heart muscle embraces 



1 Jour, of Physiol., viii, 1888, 133. 



2 Hofmeister's Beitrage, ix, 1906, 1. 



3 Lederer and Stotte, Biochem. Zeitschr., xxxv, 1910, 108. 



4 Erlandson, Zeitschr. fur phys. Chemie, li, 1907, 71. 



5 v. Fiirth, Ergebn. der Physiol., Bioch., ii, 1903, 580. 



6 Urano, Zeitschr. fur Biol, 1, 1907, 212. 



