CHAP, ii.] THE CONTRACTILE TISSUES 53 



in which it loses all the suppleness and extensibility characteristic 

 of the living irritable muscle. The causes of this loss of irritability 

 as well as the features and nature of this rigor mortis we shall 

 study in detail presently. 



The muscles and nerves of a mammal, or indeed of any warm- 

 blooded animal, lose their irritability, and the muscles become 

 rigid in a very short time (it may be a few minutes) after removal 

 from the body. Hence these are less suitable for experiments 

 than the muscles and nerves of the frog, though their general 

 phenomena are exactly the same. 



We must now attempt to study in greater detail the changes 

 which take place in a muscle and nerve during the contraction of 

 the former and the passage of an impulse along the latter, with a 

 view to the better understanding of both events. 



