GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 145 



In the case of wasting diseases rigor comes quickly, is poorly developed, and 

 passes off quickly ; when the muscles are fatigued at the time of death, as in 

 the case of a hunted animal, it comes quickly. We hear of soldiers found dead 

 on the field of battle grasping the sword, as if the muscular contractions of life 

 had been continued by the contractions of death. In the case of certain dis- 

 eases of the spinal cord and brain, too, rigor may come so rapidly that the 

 limbs may maintain the position which they had at the time of death, " cata- 

 leptic rigor," as it has been called. The coming on of rigor is particularly 

 striking in the case of diseases which, like cholera, are accompanied by violent 

 muscular cramps and lead to a rapid death. It is not uncommon, in such 

 cases, for the contractions of rigor to cause movements which may mislead a 

 watcher into supposing the dead man to be still alive. This idea is favored by 

 the fact that the body may remain warm, owing to the heat which is produced 

 in the muscles as a result of the chemical changes occurring during rigor. 

 The post-mortem muscular contractions and the rise of temperature observed 

 in such cases are only excessive manifestations of what always occurs on the 

 death of the muscle. The movements are probably due, in part, to the rapidity 

 with which the muscles contract in rigor, and in part to the fact that the 

 antagonistic muscles are not affected at the same time to the same degree. 

 Whether the contractions are partly excited by changes accompanying the 

 death of the motor nerve-cells in the central nervous system is uncertain, but 

 not impossible. Muscles are still able to respond by contractions to stimuli 

 coming to them through the nerve, even after rigor has become quite pro- 

 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. 



1 Brown-S^quard : Archives de Physiologic, 1889, p. 675. 

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