jo6 HODGE. [Vol. VII. 



inconspicuous (for adult muscle) nuclei, embedded in a little 

 granular protoplasm. 



Before proceeding it may be well to ask in which one of the 

 above elements we should expect to find changes due to meta- 

 bolic processes. From the axioms with which we started out, 

 the reticulum being the characteristic feature of the tissue, if 

 any change occurs it should occur here. We should certainly 

 not expect to find any change in the nuclei. For, aside from 

 their insignificant size, the nucleus has never been found to take 

 any part in the function of contractility. 



Any change, then, must be sought in fibrillar or interfibril- 

 lar substance. From the physiological fact, that little or no 

 increased nitrogenous waste occurs from increased muscular 

 work, we reason to a comparatively stable contractile mechan- 

 ism in muscle, comparable to the iron-work of a steam-engine. 

 We could hardly expect to find any change in a mechanism of 

 this sort from a single day's work. We are therefore confined 

 to the interfibrillar plasma, and here we undoubtedly have active 

 metabolic changes ; but the lack of definite granulation must 

 add greatly to the difficulty of demonstrating visually any proc- 

 esses which may take place. 



As might be expected, muscle tissue has been worked along 

 this line with little success. 



Du Bois-Reymond (ii, pp. 11-72) discovered, as he at first 

 supposed, marked changes due to fatigue. These consisted in 

 the breaking up of the muscle substance into irregular lumps ; 

 or, with entire loss of fibrillar structure, into fine granules. On 

 further experiment, however, he found that the phenomenon 

 could be produced by simple stretching of the muscle. It 

 occurred in equal amount whether the muscle was stretched, 

 or stretched and stimulated. So that he concludes by saying 

 (11, p. 72) "that frogs' muscles which were stimulated to com- 

 plete exhaustion, as far as the appearance of their primitive 

 fibres goes, are the same as muscles which have not been 

 stimulated." 



Again, Roth (72), in a most heroic series of experiments in 

 which muscles of frogs and rabbits were stimulated in situ con- 

 tinuously for five, ten, and even twenty days, succeeded in 

 demonstrating chiefly such changes as occur in pathological 

 degeneration of muscle. The muscle substance became vacuo- 



