GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 147 



The passing off of rigor mortis is usually accompanied by beginning 

 decomposition, and, indeed, it is generally supposed that the decomposition is 

 the cause of softening of the muscle. This is denied by certain observers, and 

 it is stated that rigor may pass off when the presence of putrefactive organisms 

 is excluded by special aseptic precautions. 



The Chemical Changes which accompany the Development of Rigor. Rigor 

 mortis is characterized by the coagulation of a part of the muscle-substance ; 

 this can be prevented by a temperature a little below C. Cold, although 

 temporarily depriving the muscle of its irritability, does not, unless extreme and 

 long-continued, kill the muscle protoplasm. Frogs can be frozen stiff and 

 recover their activity when they thaw out. Indeed, this probably happens not 

 infrequently to the frogs hibernating in holes in the banks of ponds. Since cold 

 prevents coagulation without destroying the life of the muscle protoplasm, we 

 can by its aid isolate the living muscle-substance from the nerves, blood- 

 vessels, connective tissue, and sarcolemna of the muscle, but as soon as we 

 begin to analyze it it loses its living structure. This method of obtaining 

 muscle-plasma was introduced by Kuehue 1 in the study of the muscles of frogs, 

 and was later employed with slight modifications by Halliburton 2 for the mus- 

 cles of warm-blooded animals. The blood was washed out of the vessels with 

 a stream of 0.6 per cent, sodium-chloride solution at 5 C. ; the irritable mus- 

 cles were then quickly cut out and frozen in a mixture of ice and salt at 

 12 C. The frozen muscle was then cut up finely in the cold, and a yellowish, 

 somewhat viscid, and faintly alkaline muscle-plasma was squeezed out. This 

 fluid was found to coagulate in twenty to thirty minutes at a temperature of 

 40 C. ; if the temperature were lower the coagulation was slower. The clot, 

 which was jelly-like and translucent, contracted slowly and in a few hours 

 squeezed out a few drops of serum. The coagulated material formed in the 

 clot is called myosin. It dissolves readily in dilute neutral saline solutions, 

 as a 10 per cent, solution of sodium chloride or a 5 per cent, solution of mag- 

 nesium sulphate, and its saline solutions are precipitated in an excess of water 

 or by saturation with sodium chloride, magnesium sulphate, or ammonium 

 sulphate ; it has, in short, the characteristics of a globulin. Chittenden and 

 Cummins state that it has the following composition: C 52.82, H 7.11, N 

 16.17, S 1.27, O 22.03. 



Halliburton, in studying the coagulation of muscle, followed for the sake of 

 comparison the methods which have been employed in the study of coagulation 

 of blood. He found that muscle-plasma, like blood-plasma, is prevented from 

 coagulating not only by cold, but by neutral salts, such as magnesium sulphate, 

 sodium chloride, and sodium sulphate ; and further, that the salted plasma if 

 diluted coagulates. 



The points of resemblance between the coagulation of myosin and fibrin 

 suggest a similar cause, and Halliburton succeeded in obtaining from muscles 

 coagulated by long standing in alcohol a watery extract, which greatly hastened 



1 Untersuchungen iiber das Protoplasma, Leipzig, 1864. 



2 Journal of Physiology, 1887, vol. viii. p. 134. 



