148 CHEMICAL CHANGES 



decomposed and immediately renewed from the 'blood circu- 

 lating within the muscle. This is in harmony with all Mayer's 

 principles except, perhaps, the last, which cannot be accepted 

 literally when we consider that in insects the tracheae extend 

 into the parenchyma far beyond the corpuscle-holding blood- 

 vessels, although, if we take it simply to mean that the blood 

 within the boundary of the muscle is the permanent source of 

 both the combustible matters and the oxygen, in vertebrates this 

 will be found compatible with it, taking into account the power 

 of diffusion of oxygen through the capillary walls, and, what 

 will be presently adverted to, the storing up of oxygen. Among 

 the proofs of these propositions we may notice the following : 

 The idea that force was furnished from the central nervous 

 system was soon disproved by the observation that muscles will 

 for a time contract when the connection with it is severed or 

 even when they are detached from the body. The idea that the 

 force was produced in the blood and furnished as heat or any 

 other form of force to the muscle, was also negatived by the 

 fact that the latter will still contract for a time when quite 

 empty of blood, although with blood it will do more work, and 

 that in proportion to the change produced in that blood ; there- 

 fore force is not derived from the blood per se, but the oxygen 

 and material with potential energy, whereby the muscle evolves 

 it, are. 



In the resting muscle there is a certain amount of chemical 

 change continually going on, consisting of processes which 

 ultimately involve consumption of oxygen and formation of 

 carbonic acid, but cannot be looked upon as direct oxidation, 

 but rather a formation by oxidative synthesis of a substance 

 which splits up into lactic and other acid products which are 

 neutralized by the surrounding alkaline fluids. These changes 

 produce the disengagement of active force manifested in the 

 electricjmuscle-current and also heat. In the active muscle all 

 these processes are increased and some other products are recog- 

 nized, though probably there is no really qualitative difference in 

 the action (Hermann). More oxygen is taken up and more of 

 the carbonic and lactic acids are produced, as also of the 

 alcoholic and ethereal extracts indicating the products of de- 



