1895.] On the Nature of Muscular Contraction. 431 



which, on account of the greatly-increased chemical action, a 

 chemically-caused turgescence may be accompanied to a considerable 

 extent by thermal contraction. 



Moreover, it is doubtful if we have in this case to deal with a 

 phenomenon common to all kinds of muscular fibres. Most probably 

 the mutual relations of the two processes differ with different kinds 

 of muscle. 



Hence, we may conclude that chemical contraction by turgescence 

 of the inotagmata is most likely a constant concomitant of the thermal 

 contraction of living muscle, but that compared with the latter, in a 

 single contraction, at least of striated fibres, the former is of little 

 or no consequence as regards the shortening effect. 



Ghemiotonus and Thermotonus. Both processes will probably also 

 take part in varying proportion in the tonus of muscle, which in some 

 cases will approach more to pure chemiotonus, in others more to pure 

 thermotonus. Experimental researches in this direction are wanted. 



Causes of the Relaxation of Muscle. Theoretical Considerations. Con- 

 elusion. With regard to the relaxation of muscle, according to our 

 theory this must be caused either by cooling, or by the withdrawal 

 of water from the doubly-refractive particles. Indeed, we have 

 found that doubly-refractive histological elements in general, even if 

 they be lifeless, like our violin strings, lengthen again upon cooling 

 after they have been contracted by heat, and that they lengthen 

 upon neutralisation or diffusion, after they have been contracted by 

 imbibition at an ordinary temperature. 



In a normal relaxation the muscle seems to return completely to 

 its initial state. Of course its store of energy has diminished in 

 proportion to the quantity of mechanical work and heat which has 

 proceeded from it, but, on account of the relatively infinitesimal 

 quantity of substance which is thereby consumed, this return will 

 necessarily seem to be complete even in the case of an isolated muscle. 



If we analyse the phenomena of relaxation more exactly, we 

 shall light on several possibilities, the discussion of which would 

 be very interesting with regard to the theory of muscle-life. I shall 

 restrict myself to the phenomena of the relaxation following on 

 thermal contraction. 



Here, in the first place, we might conceive that the doubly- 

 refractive inotagmata are destroyed in the thermal shortening, so 

 that each of them performs its function once only. The lengthening 

 of the muscular fibrils would then probably be caused solely by the 

 elastic powers of the parts passively extended or compressed by the 

 shortening of the inotagmata. Upon a fresh stimulation, other 

 inotagmata would, in consequence of the combustion of other ther- 

 inogenic molecules, become active, perish, &c. Through the activity of 

 the formative matter of the living muscle-fibre, the place of the lost 



