GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 101 



nounced, probably because the coagulation process attacks the different fibres 

 at different rates, and certain of the fibres are still alive and irritable after the 

 others are dead and coagulated. 



Many observers favor the view that the central nervous system influences 

 muscles after the death of the body as a whole, and by weak stimuli resulting 

 from the changes in the nerve-cells excites chemical changes in the muscles 

 which favor the coming on of rigor. 1 In proof of this it is stated that cura- 

 rized muscles enter into rigor more slowly than non-curarized. Undoubtedly 

 stimulation of the nerve, or, indeed, anything which would excite a muscle to 

 action, tends to put it in a condition favorable to the coming on of rigor; 

 whether the influence exerted by the central nervous system is more than this 

 is very questionable. 



Temperature has a marked influence on the development of rigor mortis. 

 Cold delays and warmth favors, 38°-40° C. being most favorable. Since rigor 

 is the result of a chemical change, these effects of temperature are what one 

 would have expected. Other forms of chemical change which are attributable 

 to ferment action are found to be the most vigorous at a temperature of about 

 40° C. 



In general, it may be said that rigor in warm-blooded animals comes on 

 in from ten minutes to seven hours after death, although some state that it 

 may come as late as eighteen hours. It lasts anywhere from one to six days. 

 The sooner it comes on, the sooner it goes off. The stiffness can be broken up 

 artificially by forced movements of the parts, and when thus destroyed does 

 not return, provided the rigor was complete at the time. 



The Cause and Nature of the Contraction of Rigor Mortis. — The most likely 

 explanation of the contraction of the dying muscle is that it is the result of 

 the coagulation of a part of the semi-fluid muscle-substance within the sarco- 

 lemma. This was suggested by Bruecke, and Kuehne proved that such a 

 coagulation change takes place, by showing that the semi-fluid muscle-sub- 

 stance, " the muscle-plasma," if expressed from the frozen muscle, coagulates on 

 being wanned. The coagulation is the result of a chemical change, by which 

 two proteids of the plasma, paramyosinogen and my osinogen, are converted 

 into the coagulated proteid myosin, this change being produced by the action 

 of a ferment, the myosin ferment, which is thought to be formed at the death 

 of the muscle. 



Another, though less generally accepted view, is that the contraction of the 

 muscle seen in rigor is of the same nature as ordinary muscular contractions. 3 

 Prolonged muscle contractions are observed under a great variety of condi- 

 tions (see p. 127), and there are many points of resemblance between the 

 contraction of normal and dying muscle — viz., the change of form, the pro- 

 duction of heat, the formation of sarcolactic acid, the using up of oxygen ami 

 the production of carbon dioxide, and the fact that the dying and presumably 

 coagulating muscle is, like normal contracting muscle, electrically negative 



1 Brown-Sequard : Archives de Physwlogie, 1889, p. 675. 

 'Hermann: Handbuch der Phyaiologie, 1879, Bd. i. ■ v; . 1 16. 

 Vol. II. ll 



