IONS AND MUSCULAR ACTIVITY 25 



contractility ? There is abundant evidence of 

 the splitting up of muscle constituents during 

 activity, and some evidence of their ionisation. 

 Living resting muscle has a neutral or alkaline 

 reaction ; but during activity the reaction becomes 

 acid from the development of sarcolactic and 

 carbonic acids which result from the splitting up of 

 a more complex substance or substances about the 

 time of contraction. We do not know exactly what 

 occurs during contraction. " It may be that the 

 chemical changes at the bottom of the contraction 

 do not involve the real living material of the fibre, 

 but some substance manufactured by the living 

 material. It may be that when a fibre contracts 

 it is this substance which explodes and not the fibre 

 itself. It may be a compound of carbon and 

 hydrogen which explodes, the products being sarco- 

 lactic and carbonic acids, but such is not yet 

 proved."* When a muscle-nerve preparation is 

 subjected to a shock from an induction coil a change 

 passes along the nerve to the end-plate, where it is 

 transmuted into a muscle impulse. This takes 

 place in the latent period. It is evident that the 

 electricity, whatever change it undergoes in its 

 course through the nerves, sets up an electrolytic 

 process or an " explosive decomposition which leads 

 to the formation of sarcolactic acid and disengage- 

 ment of C0 2 and heat, accompanied by a visible 

 wave of contraction in the muscle itself, "f The 

 proportion of the products bears a constant rela- 

 tionship to the energy and duration of the con- 

 traction, or vice versa, the energy of the contraction 



* Foster's "Physiology," vol. i., p. 106. f Ibi ^ P- 125 - 



