1895.] On the Nature of Muscular Contraction. 425 



instead of shorten as a result of electric stimulation. Considered 

 from other theoretical points of view, this observation seems sx> 

 paradoxical that its very validity has been questioned by some 

 physiologists ; but in the face of the direct and exact measurements, 

 of so scrupulous an observer and inquirer as Eduard Weber, we 

 have no right to do this. Moreover, Charles Richet and de Varigny 

 have confirmed the observation with different kinds of muscles of 

 Invertebrata. According to our view of the origin of muscular f orce- 

 the fact is not paradoxical at all, but might be foreseen. 



The decrease of the shortening power and the increase of extensi- 

 bility with increasing thermal contraction is, in the case of our life- 

 less doubly-refractive objects, accompanied by a decrease in the power 

 of double refraction. According to von Ebner's careful measurements, 

 confirmed by Alex. Rollett, the same thing is the case with muscles, 

 during vital contraction. We may consider this fact, too, as an 

 important proof of the fundamental resemblance between the process 

 of contraction in our model and in the muscle, and at the same time 

 as a further evidence of the existence of a causal relation between 

 double refraction and contractility in general. But it is the physi- 

 cist's task, and not the physiologist's, to penetrate further into the 

 relations between optic and elastic properties. The physiologist may 

 deem his purpose attained when he succeeds in tracing a certain vital 

 phenomenon back to processes which may also be observed in lifeless, 

 bodies. 



However, though we should, perhaps, be inclined to infer from the 

 foregoing that we have successfully acquitted ourselves of this task 

 with regard to muscular contraction, we will be careful not to over- 

 look the numerous important respects in which a muscle as a living 

 body, that is, one subjected to constant chemical transformation, 

 differs from our lifeless strings. The study of these differences is- 

 most instructive, since it throws a new light on a series of processes 

 nearly allied to contraction, especially on the phenomena of rigor 

 mortis and tonus of muscle. 



But before entering into this we shall first have to meet another 

 important objection to our views. It is based upon the absolute 

 amount of muscular force. This amount may, as you know, be very 

 high. Human muscles at the strongest tetanic contraction can 

 shorten with a force of about 10 kilogrammes to 1 sq. cm. of trans- 

 verse section. Now such a force must, according to our view, be 

 produced by a very small part only of the transverse section of the- 

 muscle. 



With a maximal tetanus, it is true, the temperature of the whole 

 muscle does rise 1 C. or more. Hence there are, perhaps, 1,000 times 

 more particles chemically active than with a moderate simple con- 

 traction, where the temperature rises O'OOl C. only. Consequently,, 



