i GENERAL PHYSIOLOGY OF MUSCLE 93 



founded on arbitrary hypotheses, is certainly more defin^e. He 

 attributes the contraction of the muscle to the electrical attraction 

 and repulsion of the doubly refracting crystalloids, the poles of 

 which undergo a change of electrical state owing to the heat that 

 is generated. On this theory the muscle shortens as its tempera- 

 ture rises ; and when the temperature of the crystalloids becomes 

 constant it lengthens, because the electrical changes subside. 

 Engelmann's experiments show, however, that the length of the 

 muscle does not depend on the rate at which the temperature 

 rises, but on the absolute temperature present at the moment in 

 the doubly refracting discs. They further show that when the 

 temperature in these discs is constant, the muscle does not 

 lengthen, but remains indefinitely shortened. 



Certain well-authenticated facts prove that there is a direct 

 association between the electrical and mechanical phenomena in 

 muscle. As long ago as 1855 Helmholtz showed by an exact 

 chronometric method that the electrical wave precedes the 

 mechanical in skeletal muscle. The same fact was demonstrated 

 in 1856 by Kolliker and H. Miiller by the experiment of secondary 

 contraction, and by Bernstein with his differential rheotome. In 

 the nerve-fibres, in which no sign of mechanical phenomena can 

 be detected, and little heat development or chemical activity, 

 electrical phenomena similar to those of the muscle occur, which 

 proves them to be quite independent of the phenomena of con- 

 tractility. Certain important researches of Biedermann (1880) 

 favour the same conclusion, since they prove that frog muscles 

 which have lost their power of contracting by imbibition of water 

 or the effect of ether vapour preserve their electrical excitability 

 and capacity for conducting intact. From this Biedermann 

 concludes that the capability of actively changing its form at the 

 seat of direct stimulation is not an indispensable condition of the 

 excitation of muscle. 



The independence of the electrical phenomena from muscular 

 contractility is also demonstrated by the fact that the majority 

 of electric and pseudo-electric organs develop at the expense of 

 the striated muscle fibres, and that during this development, 

 according to Ewart, contractility is gradually lost, while the 

 electromotive function develops in proportion. According to 

 Baglioni (1906) the chemical composition of the electrical organs 

 differs fundamentally from that of the muscles. 



On the strength of all these facts Engelmann founded his 

 hypothesis that in muscle the particles on which the development 

 of the electrical phenomena depends are quite distinct from those 

 which supply heat by combustion (thermogenic), and those which 

 subserve mechanical work (inogenic particles). 



The first are solely concerned with excitation and its con- 

 duction and propagation, as Hermann also concluded from the 



