CADAVERIC RIGIDITY. 947 



tends to the arms, and finally, to the legs, disappearing in the same order of succession. 

 The stiffening of the muscles is due to a sort of coagulation of their substance, analogous 

 to the coagulation of the blood, and is probably attended with some shortening of the 

 fibres ; at all events, the fingers and thumbs are generally flexed. That the rigidity is 

 not due to coagulation of the blood, is shown by the fact that it occurs in animals killed 

 by hemorrhage. 



According to John Hunter, the blood does not coagulate nor do the muscles become 

 rigid in animals killed by lightning or hunted to death ; but it is a question, in these 

 instances, whether the rigidity does not begin very soon after death and continue for 

 a brief period, so that it may escape observation. As a rule, rigidity is less marked in 

 very old and in very young persons than in the adult. It occurs in paralyzed muscles, 

 provided they have not undergone extensive fatty degeneration. 



Under ordinary conditions of heat and moisture, as the rigidity of the muscular sys- 

 tem disappears, the processes of putrefaction commence. The various tissues, with the 

 exception of certain parts, such as the bones and teeth, which contain a large proportion 

 of inorganic matter, gradually decompose, forming water, carbonic acid, ammonia, etc., 

 which pass into the earth and the atmosphere. The products of decomposition of the 

 organism are then in a condition in which they may be appropriated by the vegetable 

 kingdom. 



