534 HANDBOOK OF PHYSIOLOGY. 



energy. It has been suggested by Herman that muscular activity de- 

 pends upon the splitting up and subsequent re-formation of a complex 

 nitrogenous body, called by him Inogen. When this body so splits up 

 there result from its decomposition, carbon dioxide, sarcolactic acid, 

 and a gelatino-albuminous body. Of these the carbon dioxide is carried 

 away by the blood stream; the albuminous substance and possibly the 

 acid, at any rate in part, go to re-form the inogen. The other materials 

 of which the inogen is formed are supplied by the blood ; of these mate- 

 rials we know that some carbohydrate substance and oxygen form a part. 

 The decomposition, although taking place in resting muscle, reaches a 

 climax in active muscle, but in that condition the destruction of inogeu 

 largely exceeds restoration, and so there must be a limit to muscular 

 activity. But this is not the only change going on in muscle, there are 

 others which aifect the nitrogenous elements of the tissue, and from 

 them result the nitrogenous bodies of which kreatin is the chief; these 

 changes may be unusually large during severe exercise. 



It has been further suggested that, as myosin is undoubtedly formed 

 in rigor mortis, when the muscle becomes acid and gives off carbon 

 dioxide, that myosin is also formed when muscle contracts, and that, in 

 other words, contraction is a condition akin to partial death. The 

 electrical reaction appears to justify this; both contracted and dead 

 muscle are negative to living muscle, when at rest. What happens to 

 the myosin which is formed when muscle contracts, if this view be the 

 correct one, is unknown. Halliburton suggests that the myosin which 

 can be made to clot and unclot easily enough outside the body, is able 

 to do the same thing in the body. It is possible that the clotting of 

 myosinogen which is supposed to occur during contraction, is not of the 

 same intensity or extent as that which occurs post mortem. The rela- 

 tion of the hypothetical inogen to the rest of the muscle-fibre is unde- 

 termined. It may be that the inogen is formed by the activity of the 

 muscle-protoplasm, and stored up within itself, and that during rest of 

 muscle it is gradually used up, whereas in activity it is suddenly and 

 explosively decomposed. In the rest of the fibre the nitrogenous meta- 

 bolism continues much the same during rest as during activity. 



Again, histologically, the question as to which is the contractile and 

 which is the non-contractile part of muscle, has been, as we have seen 

 (p. 86 et seq.), a matter of much controversy. 



As regards nervous metabolism, we have little knowledge of anything 

 except the electrical phenomena which have been already considered. 

 For the maintenance of nervous irritability, oxygen is required ; to form 

 this, it has been suggested that the nervous impulse is the result of 

 processes of an oxidative character, etc. The chief seat of the metabo- 



