592 MOTION. 



nerves for some time after death, the period being longer 

 in cold-blooded than in warm-blooded Vertebrata, and 

 shorter in birds than in Mammalia. It would seem as if 

 the more active the respiratory process in the living animal, 

 the shorter is the time of duration of the irritability in the 

 muscles after death ; and this is confirmed by the comparison 

 of different species in the same order of Vertebrata. But 

 the period during which this irritability lasts, is not the 

 same in all persons, nor in all the muscles of the same 

 persons. In a man it ceases, according to Nysten, in the 

 following order : first in the left ventricle, then in the 

 intestines and stomach, the urinary bladder, right ventricle, 

 oesophagus, iris; then in the voluntary muscles of the 

 trunk, lower and upper extremities; lastly in the right 

 and left auricle of the heart. 



After the muscles of the dead body have lost their irri- 

 tability or capability of being excited to contraction by the 

 application of a stimulus, they spontaneously pass into a 

 state of contraction, apparently identical with that which 

 ensues during life.* It affects all the muscles of the body; 

 and, where external circumstances do not prevent it, com- 

 monly fixes the limbs in that which is their natural posture 

 of equilibrium or rest. Hence, and from the simultaneous 

 contraction of all the muscles of the trunk, is produced a 

 general stiffening of the body, constituting the riff or mortis 

 or post-mortem rigidity.} 



* If, however, arterial blood be made to circulate through the body 



or through a limb, the post-mortem contraction of the muscles thus sup- 



* plied with blood, may, as Dr. Brown-Sequard has shown, be suspended, 



and the muscles again admit of contracting on the application of a 



stimulus. 



f It should be stated here, however, that the generally accepted ex- 

 planation of the state of the muscles during rigor mortis, namely, that it 

 is due to contraction of the fibres, as in strong action during life, is denied 

 by some physiologists, who maintain that the condition of the muscles is 

 not due to contraction at all, but is caused by a kind of coagulation of 

 the inter-fibrillar juices. This idea has been of late especially sup- 

 ported by Dr. Norris (see Camb. J. of Anat. and Phys., Part I.). 



