96 CHEMISTRY OF MUSCLE. [BOOK i. 



as rigor mortis. The occurrence of rigor mortis, or cadaveric rigidity, 

 as it is sometimes called, which may be considered as the token of 

 the death of the muscle, is marked by the following features. The 

 living muscle possesses a certain translucency, the rigid muscle is 

 distinctly more opaque. The living muscle is very extensible and 

 elastic, it stretches readily and to a considerable extent when a 

 weight is hung upon it or when any traction is applied to it, but 

 speedily and, under normal circumstances, completely returns to 

 its original length when the weight or traction is removed ; as we 

 shall see however the rapidity and completeness of the return 

 depends on the condition of the muscle, a well nourished active 

 muscle regaining its normal length much more rapidly and com- 

 pletely than a tired and exhausted muscle. A dead rigid muscle 

 is much less extensible and at the same time much less elastic ; 

 the muscle now requires considerable force to stretch it, and when 

 the force is removed, does not, as before, return to its former 

 length. To the touch the rigid muscle has lost much of its former 

 softness, and has become firmer and more resistent. The entrance 

 into rigor mortis is moreover accompanied by a shortening or 

 contraction, which may, under certain circumstances, be con- 

 siderable. The energy of this contraction is not great, so that any 

 actual shortening is easily prevented by the presence of even a 

 slight opposing force. 



Now the chemical features of the dead rigid muscle are also 

 strikingly different from those of the living muscle. 



59. If a dead muscle, from which all fat, tendon, fascia, and 

 connective tissue have been as much as possible removed, and 

 which has been freed from blood by the injection of * normal ' saline 

 solution, be minced and repeatedly washed with water, the washings 

 will contain certain forms of albumin and certain extractive bodies, 

 of which we shall speak directly. When the washing has been 

 continued until the wash-water gives no proteid reaction, a large 

 portion of muscle will still remain undissolved. If this be treated 

 with a 10 p. c. solution of a neutral salt, ammonium chloride being 

 the best, a large portion of it will become dissolved ; the solution 

 however is more or less imperfect and filters with difficulty. If the 

 filtrate be allowed to fall drop by drop into a large quantity of 

 distilled water, a white flocculent matter will be precipitated. 

 This flocculent precipitate is myosin. Myosin is a proteid, giving 

 the ordinary proteid reactions, and having the same general 

 elementary composition as other proteids. It is soluble in dilute 

 saline solutions,' especially those of ammonium chloride, and may 

 be classed in the globulin family, though it is not _so soluble as 

 paraglobulin, requiring a stronger solution of a neutral salt to 

 dissolve it ; thus while soluble in a 5 or 10 p. c. solution of such a 

 salt, it is far less soluble in a 1 p. c. solution, which as we have 

 seen readily dissolves para'globulin. From its solutions in neutral 

 saline solution it is precipitated by saturation with a neutral 



