594- MOTION. 



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 ex- 

 tremities, extending from above downwards ; and lastly, 

 reaches the lower limbs ; in some rare instances only, it 

 affects the lower extremities 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 ex- 

 tremities, 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 con- 

 firmed 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 capacity 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 the bodies of persons exhausted by 

 chronic diseases ; and its tardy onset and long continuance 

 after sudden death from acute diseases. In some cases of 

 sudden death from lightning, violent injuries, or paroxysms 

 of passion, rigor mortis has been said not to occur at all ; 

 but this is not always the case. It may, indeed, be doubted 

 whether there is really a complete absence' of the post- 

 mortem rigidity in any such cases ; for the experiments of 

 M. Brown- Sequard with electro-magnetism make it pro- 

 bable that the rigidity may supervene immediately after 

 death, and then pass away with such rapidity as to be 

 scarcely observable. Thus, he took five rabbits, and 

 killed them by removing their hearts. In the first, rigidity 



