588 A MANUAL OF PHYSIOLOGY 



production, and this is evidently related to its action in hastening 

 the onset of rigor. 



In a human body rigor generally appears not earlier than 

 an hour, and not later than four or five hours, after death. 

 In exceptional cases, however, it may come on at once, and 

 the annals of war and crime contain instances where a man 

 has been found after death still holding with a firm grip the 

 weapon with which he had fought, or which had been thrust 

 into his hand by his murderer. It is related that after one 

 of the battles of the American Revolutionary War some of 

 the dead were found with one eye open and the other closed 

 as in the act of taking aim. A high temperature favours 

 a rapid onset ; a body wrapped up in bed will, other things 

 being equal, become rigid sooner than a body lying stripped 

 in a field. Muscular exhaustion, as we have said, is another 

 favouring condition : hunted animals and the victims of 

 wasting diseases go quickly into rigor. It is a rule, but not 

 an invariable one, that rigor, when it comes on quickly, is 

 short, and lasts longer when it comes on late. All the 

 muscles of the body do not stiffen at the same time ; the 

 order is usually from above downwards, beginning at the 

 jaws and neck, then reaching the arms, and finally the legs. 

 After two or three days the rigor disappears in the same 

 order. The position of the limbs in rigor is the same as 

 at death ; the muscles stiffen without any marked con- 

 traction. This can be strikingly shown on a newly-killed 

 animal by cutting the tendons of the extensors of one foot 

 and the flexors of the other ; when natural rigor comes on 

 the feet remain just as they were. If heat rigor, however, 

 is caused, the one foot becomes rigid in flexion and the other 

 in extension; and the contraction -force is considerable, 

 although not so great as that of an electrical tetanus in a 

 living muscle. 



The Removability of Rigor. It has been asserted that rigor 

 can be removed and excitability restored. After interrupt- 

 ing the circulation in the hind-legs of rabbits by compres- 

 sion or ligation of the abdominal aorta (Stenson's experi- 

 ment), and so causing the muscles to become rigid, Brown- 

 Sequard saw them recover their irritability when the blood 



