42 



CONTRACTILITY 



as the result of prolonged tonic contraction only. The 

 manner in which carbohydrates are broken down and the 

 significance of lactic acid will be dealt with below. 



5. The Electrical Changes 



If two non-polarisable electrodes are placed one on the 



Fig. 5. — Showing three stages in the diphasic variation. 



surface, the other on the cut end of a muscle and connected 

 with a galvanometer, the instrument shows a current 

 passing from the intact surface through the galvanometer 

 to the cut surface ; the injured part, that is to say, is electro- 

 negative to any other part. This electrical effect is pro- 

 duced even by the injury involved in the most careful 



