92 THE HUMAN BODY 



solid form cannot be digested: they may thus help the stomach 

 over a crisis, but are not, even the best of them, to be depended on 

 as anything but temporary substitutes for other food; or in some 

 cases as useful additions to it. 



Rigor Mortis. During life and for a certain time after general 

 death the muscles are soft, translucent, extensible and elastic, and 

 neutral or feebly alkaline in reaction; after a period which in warm- 

 blooded animals is brief (varying from a few minutes to three or 

 four hours) they gradually become harder, more opaque, less ex- 

 tensible and less elastic, and distinctly acid in reaction. The 

 result of these changes is the well-known cadaveric rigidity or 

 rigor mortis. It was formerly very generally believed that the 

 cause of rigor is the change of soluble myogen and the myosin to in- 

 soluble myogen fibrin and myosin fibrin. Quite recently, how- 

 ever, some physiologists have called attention to the strong prob- 

 ability that death stiffening may be due to the considerable 

 production of lactic acid which is known to accompany the death 

 process. In support of their view may be cited the well-known 

 tendency of animals or men killed suddenly in the midst of violent 

 exertion to stiffen very quickly. Men killed in battle often re- 

 tain the postures in which death overtook them. Hard muscular 

 work involves a large production of lactic acid, a condition favor- 

 able according to the view quoted, to a prompt onset of rigor. 



