EIGOR MORTIS. 465 



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 irrita- 

 bility or capability of being excited to contraction by the ap- 

 plication of a stimulus, they spontaneously pass into a state of 

 contraction, apparently identical with that which ensues during 

 life. 1 It affects all the muscles of the body ; and, where ex- 

 ternal circumstances do not prevent it, commonly 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 rigor mortis or post-mortem rigidity} 



The muscles are not affected exactly simultaneously by the 

 post-mortem contraction, but rather in succession. It affects 

 the neck and lower jaw first ; next, the upper extremities, ex- 

 tending from above downwards ; and lastly, reaches the lower 

 limbs ; in some rare instances only, it affects the lower ex- 

 tremities before, or simultaneously with, the upper extremities. 

 It usually ceases in the order in which it began ; first at the 

 head, then in the upper extremities, and lastly in the lower 

 extremities. According to Sommer, it never commences 

 earlier than ten minutes, and never later than seven hours, 

 after death ; and its duration is greater in proportion to the 

 lateness of its accession. According to Schiffer, and others 

 have confirmed the truth of his observation, heat is developed 

 during the passage of a muscular fibre into the condition of 

 rigor mortis. 



Since rigidity does not ensue until muscles have lost the ca- 

 pacity of being excited by external stimuli, it follows that all 

 circumstances which cause a speedy exhaustion of muscular 

 irritability, induce an early occurrence of the rigidity, while 

 conditions by which the disappearance of the irritability is 

 delayed, are succeeded by a tardy onset of this rigidity. 

 Hence its speedy occurrence, and equally speedy departure in 



1 If, however, arterial blood be made to circulate through the 

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

 thus supplied with blood, may, as Dr. Brown-Sequard has shown, be 

 suspended, and the muscles again admit of contracting on the appli- 

 cation of a stimulus. 



2 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 interfibrillar juices This idea has been of 

 late especially supported by Dr. Norris (see Camb. Journal of Anat- 

 omy and Physiology, Part I). 



