418 HERMANN. [BOOK I. 



As to the supposititious substance itself, all that direct observation 

 suggested was that it must be of such a nature as to yield carbon 

 dioxide and some free acid, probably lactic ; but by reflecting upon 

 the analogies of contraction and rigor, Hermann was led to assign to it 

 a very complicated structure. The resemblances of contraction and 

 rigor are manifold. In each there occurs a shortening, thickening, and 

 small reduction of bulk of the muscle ; and a mechanical force is 

 developed to each, although at very different rates. Both processes 

 are associated with an evolution of heat ; and we may now add that 

 contracting muscle and muscle becoming rigid assume the same electric 

 potential in reference to living and resting muscle. With regard to 

 their chemical changes, both processes are independent of the oxygen of 

 the surrounding medium, and both are followed by the appearance of 

 a free acid and the formation of carbon dioxide. Further, there is this 

 relationship between the two in the case of excised muscles, that 

 the more free acid and carbon dioxide are produced by the previous 

 tetanus of the muscle the less are generated on subsequently passing 

 into rigor. Moreover, phenomena are known which seem to be most 

 naturally regarded as intermediate states between contraction and 

 rigor. If a fatigued muscle receives a sharp stimulus, as from a 

 sudden blow, a local (idio-muscular) contraction is produced which 

 lasts for a long time ; and if such an exhausted muscle be repeatedly 

 stimulated it may pass at once into true rigor. 



If, then, contraction so closely resembles rigor, may we not consider 

 it as a transitory form of rigor, and assume that we have in contraction 

 what undoubtedly occurs in rigor, viz. the separation of a coagulum of 

 myosin ? In rigor the coagulum at once passes to a condition of con- 

 * tracted clot : here, therefore, the analogy must end ; for in normal 

 irritable muscle the clot never goes beyond the gelatinous stage. 



Hermann's hypothesis may thus be summed up : The chemical 

 substratum of muscular activity is the falling to pieces of a complex 

 nitrogenous body, which has been called Inogene substance. The pro- 

 ducts of the decomposition include carbon dioxide, a fixed acid, and a 

 gelatinous albuminous body, of which the first is cast into the blood- 

 current, while the last, and possibly the second also, help to build 

 up again the original compound. The decomposition is constantly 

 occurring, even during the repose of muscle ; but in such circumstances 

 restoration keeps pace with destruction. In contraction, on the 

 contrary, destruction largely exceeds restoration. The blood supplies 

 to muscle the non-nitrogenous matter and the oxygen needed for 

 the reproduction of Inogene substance. 



Along with the chemical changes of Inogene substance, other 

 changes occur in the regeneration of muscle itself. These affect the 

 nitrogenous as well as the non-nitrogenous elements of the tissue, 

 and help to swell the nitrogenous excreta. In cases of severe exertion 

 it is not improbable that these changes may be unusually large ; and 

 this especially would be the case were individual muscular fibres to 

 become rigid and stand in need of absorption and removal. 



