522 



NATURE 



[March 28. 1895 



thermometer is placed in the water in such a position that it 

 will remain at a distance of about I cm. iiom the spiral wire. 



The string is now obseived fcr some minutes at a tension of 

 25 or 50 grammes and at a constant temperature until no 

 further change in the position of the lever can be discerned. 

 If we now close for some seconds Ihe circuit of the battery 

 through Ihe spiral, the lever rises. Ufoti opining the circuit, it 

 falls. The thermometer in the ^lass indicates a hardly fercepttble 

 rise in temperature, or no rise at all. 



■\Ve see the doubly-refractive string of our model corresponds 

 to the doubly-refractive muscular particle, which we suppose 

 to be the seat of the force of contraction, and therefore may be 

 called " inotasma" ; the water in the glass represents the 

 watery isotropic substance round the inolagma, doing duty as 

 refrigerant ; the spiral wire supplies the place of the chemically 

 active t/:ermogenii- molecules ; the closure of the galvanic cir- 

 cuit corresponds with the process of the stimulation of the 

 muscular element. 



The movements may be inscribed on a rotating cylinder. 

 We then obtain curves of the same character as contraction- 

 cur\-5 of muscles. 



Fic. 3. 



Such a (T^on/o^jraOT presents, like a myogram, three periods, 

 viz. : — 



(1) A period of latent energy, the duration of which, just as 

 with the muscle, decreases with the increasing energy of the 

 stimulus (;.<'., with the intensity -and duration of Ihe electric 

 current), with rising temperature and with decreasing load. 



(2) A peiiod of augmenting energy, in which contraction 

 lakes place with a rapidity, first increasing, afterwards diminish- 

 ing, the contraction being, within certain limits, more rapid 

 and the larger in extent the stronger the stimulalion. 



(3, A period of declining eneigy, in which the string relaxes 

 with a gradually decreasing rapidity. 



further Coiiiparalive Researches on the Thermal Contraction 

 of Lijeiess Double Kefractivc Bodies and the Physiological Con- 

 traction of Muscle. — The points of resemblance between our 

 model and a muscle extenil much further yet, and amongst 

 other points to peculiarities which seem to bear important testi- 

 mony to the identity of the mechanical process in the two cases. 



Such a resemblance I find, in the first place, in the fact that 

 the strength of the shorteuitii; fcucr, dix eloped ly a certain 

 stimulus, increases with the /f a. /within certain limits. Holh 

 muscle and string present the paiadoxical phenomenon that, 

 under a stimulus of equal energy, heavier weights may be lifted 

 higher than lighter ones. 



Neither the chemical nor the electrical hypothesis of the 

 origin of muscular force can give a suflicienl explanation of this 

 fact. On the basis of our theory, on the contrary, it can be 

 predicted, because cveiy influence which aufmenis the doubly- 

 refractive ix)wer must laise the power of contraction. 



Now, von Kbner has j^roved experimentally that Ihe force of 

 double refraction of tcndor.s and also, between certain limits, of 

 muscles, increaics willi the load. The same is the cise with 

 fibres of elastic tissue an<l with caoutchouc, and with these also 

 the contractile power incrca.'es with the load. The differences 

 of force thus depending on the load are by no means insignifi- 

 cant. 



Connected with this point is another fact, viz. that the force 

 of shortening produced in our model by means of a given rise 

 of temperature, il Ihe smaller Ihe more the string has already 

 contracted. The maximum of force is, at all events, displayed 

 when the extension of the siring is brought by the whole load 

 )>cing applied at once at the very beginning of the healing, not 

 after the string has already contiaclcd \>itli a smaller load. 



The very same thing, as Schwann's experiments showed 

 many yeais ago, holds good of muscle. On the hypothesis of 

 chemical attraction we should decidedly expect the reverse: 

 viz. increase of force with an increasing mutual approach of 

 the combining molecules ; so also in the same way on every 

 other hypothesis which pronounces contraction to be caused by 

 atlra ctive powers increasing in inverse proportion to the square 

 of distance. 



In the fact discovered by Schwann, Johannes Miiller thought 

 he had found a refutation of the old electro-dynamic hypothesis 

 of Trevost and Dumas, as well as a valid reason for assuming a 

 fundamental rel.ition between the vit.il power of contraction and 

 physical elasticity. 



Ilowevcr, as Hermann has observed, we might in this case 

 get over the difficulty by supposing that between or in the length 

 of the parts attracting e.ich other, there are elastic layers oppos- 

 ing that altiaction with incre.ising force. It is evident that our 

 view of the matter does not require such an auxiliary hypothesis, 

 because, in accordance with Eduard Weber, we regard muscular 

 contraction as only a special case of elastic shortening. 



A closer experimental comparison of the dianges undergone, 

 on the one hand, by the ekisticity of our string during thermal 

 shortening, and, on the other h.ind, by muscular elasticity during 

 jihysiological contraction, will teach us that, in each case, the 

 changes are of exactly the same kind. 



.-Vs regards striated muscles, it was Eduard Webev who, by 

 his classic researches, established that their extensibility in- 

 creases during contraction. The same is now proved to hold 

 good of strings and other organic doubly-refractive substances 

 during thermal shortening. 



The curve of lengthening of all these objects inclines more 

 sharply towards the ,-ibscissK of the loads the higher the tempera- 

 ture. Both curves converge, and may finally even cross, i.e. a 

 certain load being exceeded we do not get contraction but 

 lengthening as the efTect of heating. 



This circumstance explains the fact, sometimes observed by 

 E. Weber, that living, tired, heavily-loaded muscles of frogs, 

 lengthen instead of shorten as a result of electric stimulalion. 

 Considered from other theoretical points of view, this obser- 

 vation seems so paradoxical that its very validity has been 

 (luestioned by some ]>hysiolrgists, 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. 

 According to our view of the origin of muscular force this fact 

 is not paradoxical at all, but might be foreseen. 



The decrease of the shortening power and the increase of 

 extensibility with increasing thermal contraction is, in the case 

 of our lifeless doulil) -refractive objects, accompanied by a de- 

 crease in the power of double refraction. According to von 

 Ebrer's careful nie:isuiemcnls, the same thing is the case with 

 muscles during vil.il contraction. We may consider this fact, 

 too, as an important proof of the fundamental resembhince 

 between the process of contraction in our model and in the 

 muscle, and at the same lime as a further evidence of the exist- 

 ence of a causal relation 1 ctween double refraction and con- 

 tiactility in geneial. lUit it is the physicist's task, and not the 

 physiologist's, to j enettate funher into the relations between 

 optic and clastic piopcrties. The physiologist may deem his 

 purpose attained when be succeeds in tracing a certain vital 

 phf nomeron back to pioce.sses which may .ilso be observed in 

 lifeless bodies. 



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

 from Ihe foregoing that we have successfully acquitted ourselves 

 of this task with regard to muscular contraction, we will be 

 careful not to overlook the numerous im]K>rtant respects in 

 which a muscle as a living body, that is, one subjected to 

 constant chemical transfoimation, differs from our lifeless 

 strings. The study of these difl'erences is most instructive, 

 since il throws a new lighl on a series of processes nearly allied 

 to contraction, especially on the phenomena of rigor mortis Md 

 tonus of muscle. 



Hut 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 

 krow, be very high. Human muscles at the .strongest tetanic 

 contiaction can shorten with a force of about lo kilogrammes to 

 I sq. cm. transverse section. Now such a force must, according 

 lo our view, be produced by a small part only of the transverse 

 see'ion of the muscle. 



With a maximal tetanus, it is tiuc, the Icnipcraluic of the 



NO. 1326, VOL. 51] 



