STRIATED MUSCLE. 71 



elasticity, witness the pain and difficulty experienced in 

 extending the forearm, after it has been long kept in a 

 sling. 



The muscles of a corpse are at first flabby and extensible, 

 preserving any shape which may be given them ; still they 

 are slightly, but imperfectly, elastic ; later, they enter the 

 state known as that of cadaveric (corpse-like) rigidity, when 

 immense force is required to stretch them out, and, being once 

 stretched, they can no longer regain their original form, and 

 thus become strongly and imperfectly elastic. This cadaveric 

 rigidity was formerly attributed to coagulation of the fibrin of 

 the blood (J. Miiller) ; but it is now generally supposed to be 

 owing to the coagulation of the myosin, or of its derivative, 

 the syntonin (Kiihne), an albuminoid substance, which coag- 

 ulates spontaneously, and closely resembles the fibrin of the 

 blood. The muscular fluid coagulates by heat; thus the 

 cadaveric rigidity of a muscle may be produced instantane- 

 ously, by immersing it in a fluid at a temperature of 45 c. 

 (See farther on, p. 82.) 



We see, thus, that slight and perfect elasticity is, up to a 

 certain point, characteristic of the life of the muscle ; and 

 that it differs entirely, in this respect, from the elasticity of 

 the ligaments, of the bones, and, above all, of the elastic 

 tissue; since their elasticity remaining always the same, 

 depends only on the mechanical arrangement of the fibres of 

 which these tissues are composed, and is thus purely physi- 

 cal. This cannot be said of the elasticity of the muscle; 

 neither can we look upon it as an essentially vital property, 

 for it appears to depend principally upon the chemical com- 

 position of the muscle. In fact, by injecting hot water (ex- 

 periment of Brown-Sequard), or defibrinated blood, or serum, 

 or even any simple alkaline liquid, into the arteries of an 

 animal lately killed, it may be for a time preserved from this 

 rigidity, which is brought on by the acidity of the muscle, 

 and is opposed by its alkalinity. If, for instance, the arm 

 being in repose, and the tendon of the biceps cut, we find 

 that it immediately shrinks a little ; and, having been pre- 

 viously slightly extended, assumes its natural form only by 

 the natural distance of its points of insertion, and, conse- 

 quently, exerts upon these latter only slight traction. This 

 is called the tonicity of the muscles; but we see that it is not 

 a special property of the muscle, but is only the result of its 

 elasticity, brought into play by its insertions, the distance of 

 which prevents it from perfectly assuming its proper form; 



