152 THE SPINAL CORD AND CEREBELLUM 



more. Hence the venous blood which comes forth 

 from it becomes immediately black. 



We know that this change of colouration is the 

 indication of important chemical mutations. Thus 

 the venous muscular blood which, in the state of 

 repose, contains only 6-75 per cent, of carbonic acid 

 more than the arterial blood, contains 10'79 per cent, 

 after the contraction. 



From the above remarks it will be seen that the 

 functional activity of muscles is indissolubly linked to 

 an increase of nutritive activity — to a higher degree, 

 that is to say, of chemical change. If, therefore, we 

 are justified in connecting the cerebellum with the 

 contractile portion of muscular activity, as we certainly 

 are if we regard it as an organ of equilibration; can 

 we logically put aside the chemical portion of it and 

 say. To this the connection does not apply ? The 

 matter will appeal to us more strongly if we reflect 

 for a moment. The contraction is primarily due to 

 the motor cells of the cerebral cortex. The part 

 played by the cerebellum is not — Farrier has shown 

 this — save in quite a secondary manner, of a co-ordina- 

 ting nature.* 



Nor can we speak of it as anything else of a tangible 

 nature, unless it be an increasing or reinforcing 

 agency, acting through the medium of the remaining 

 element in muscular activity, namely, chemical change. 

 If this be true of the muscular system, it is probably 

 so in the case of all the tissues the nervous supply of 

 * See p. 133. 



