50 PHYSIOLOGY OF MUSCLE AND NERVE 



and shortening with the help of a violin string which he first passed through a coil 

 of platinum wire and then attached under some tension to a writing lever. If this 

 string was immersed in water and then subjected to heat by passing an electrical 

 current through the wire, it shortened very considerably. The subsequent dis- 

 continuance of the current permitted the string to regain its original length. The 

 curves recorded in this manner are very similar to those obtained with muscle 

 preparations under ordinary conditions of experimentation. 



Ranvier 1 agrees with Engelmann in so far as he believes that the anisotropic 

 substance is the only contractile part of the fiber. He holds, however, that the 

 anisotropic discs lose water on contraction which is transferred to the interfibrillar 

 substance. Schafer 2 adheres to Engelmann's hypothesis and states further that 

 the anisotropic substance is permeated by minute channels which run parallel to 

 the axis of the fiber and serve to accommodate isotropic material. In consequence 

 of the filling of these canaliculi the individual segments or prisms of the anisotropic 

 substance are forced farther apart, causing a widening of the fiber on contraction. 



Absorption is also the principle of the hypothesis of McDougall. 3 It is be- 

 lieved that the sarcostyles or fibrillse of striated muscle are constructed in such a 

 way that their distention immediately produces a reduction in their length. This 

 distention is assumed to take place as a result of an influx of the sarcoplasmic fluid 

 which surrounds them. Meigs 4 has applied this conception to smooth muscle and 

 claims that its contraction is dependent upon the passage of fluid from the cell 

 into the interstitial spaces. 



A hypothesis has also been formed by Miiller 5 which attributes muscular 

 contraction to an electrical attraction and repulsion of doubly refracting crystal- 

 loids. In consequence of a production of heat, these bodies change their poten- 

 tial, relaxation resulting when the polarity subsides owing to the equalization of 

 the temperature. It is a well-known fact that muscular contraction, as well as 

 any other activity of protoplasm, is associated with electrical variations, but these 

 changes have been proved to be quite independent of contractility. 6 All these 

 hypotheses are very indefinite. Based upon the work of Berthold 7 a hypothesis 

 has been formulated by Verworn 8 which holds that the chemical changes in muscle 

 result in alterations in the surface tension of the isotropic and anisotropic discs. 

 In consequence of these- variations, the histological constituents of muscle change 

 their power of cohesion and adhesion and hence, their shape and position. Jenson 9 

 has put forward the so-called coagulation-hypothesis which bases the contraction of 

 muscle upon changes in the aggregate condition of the sarcoplasm. In accordance 

 with this view, its relaxation is not regarded as a passive phenomenon, but is said 

 to occur in consequence of processes the reverse of the former. 



It is to be noted especially that the contraction of muscle re- 

 quires merely an internal readjustment of its constituents and does 

 not involve changes in its volume which could only be had by a 

 transfer of material from and to other tissues. This fact may be 

 proved by placing a muscle in a glass receptacle filled with boiled 

 saline solution, and equipped with a capillary tube in which the water 



1 Lecons d'anat. ge"n. sur le syst. muse., Paris, 1880. 



2 Proc. Royal Society, xlix, 1891. 



8 Journ. of Anat. and Physiol., xxi, 1897 -, 410; and xxii, 1898, 187. 



4 Am. Journ. of Physiol., xxii, 1908, 476; also Hurthle, Pfluger's Archiv, cxxvi, 

 1909, 1. 



5 Theorie der Muskelkontraktion, Leipzig, 1891. 



6 Helmholtz (1855) and Biedermann, Elektrophysiol., Jena, 1895. 



7 Studisn iiber die Protoplasma Mechanik, Leipzig, 1886. 



8 Allg. Physiologic, Jena, 1910; and Saleotti, Zeitschr. fur Allg. Physiol., 

 vi, 1906. 



9 Pfluger's Archiv, cxxxvii, 1901, 367. 



