40. THE MENDEL JOURNAL 



contractile material of a more fluid nature. The 

 contractile substance is arranged as longitudinal 

 fibrils embedded in interfibrular matter."* 



Oxygen and a carbo-hydrate in the form of glycogen 

 are essential to muscular life and action. A stock of 

 both, but principally of oxygen, is taken up and 

 stored in the essential constituents of the muscle 

 fibre. These constituents are broken down during 

 muscular contraction, and more slowly during rest, 

 carbon dioxide and lactic acid being the end pro- 

 ducts. Kanke has shown that the exhausted muscles 

 of a frog can be restored by washing out the vessels 

 with physiological salt solution. He claims that it 

 is the removal of carbon dioxide and lactic acid, the 

 products of contraction, which immediately restored 

 the muscle. The injection of arterial blood, or of an 

 oxidising agent, like potassium permanganate, into 

 the vessels of an exhausted muscle also causes 

 restorationf. 



When a muscle fibre is stimulated it increases in 

 cross sectional area, but the volume remains con- 

 stant, contraction commencing in the middle of the 

 fibre and passing to the ends. 



The Varieties of Muscle Fibres in the Race 



Horse. 



So far we have considered the structure and pro- 

 perties of what may be termed typical striped muscle 

 fibre. But it has been clearly established that there 

 are two varieties of striated muscle, namely pale and 



* Stewart. t Kroneeker. 



