March 28, 1895] 



NATURE 



523 



whole muscle does rise l° C. or more. Hence there are, 

 perhaps, looo times more particles chemically active than with 

 a moderate simple contraction, where the temperature rises 

 O'OOl" C. only. Consequently, during such a tetanus, a much 

 greater part of the muscular substance — perhaps loao times as 

 much — will be healed to such a degree as is required for an 

 obvious contraction of the inotagmata. But even in this case 

 the greater pait of the whole substance will be only moved 

 passively. 



Can such very important mechanical powers as we are 

 obliged to assume in the inotagmata be evolved through the 

 thermical contraction of doubly-refractive boJies? Do we not, 

 as Fick says, in making such a supposition, go too far beyond 

 the bounds of legitimate analogy ? 



Of course nothing but the measurement of the force; de- 

 veloped by lifeless doubly-refraclive bodies under thermal con- 

 traction will decide this question. I have made many of these 

 measurements on variojs objects, and I think the results afTord 

 us a refutation of the objection. Strings, moist but not yet 

 contracted through lying in water, with a diameter of 07 mm., 

 and loaded with i kilogramme, lif ed up the weight in a per- 

 ceptible degree when rapidly healed up to 130' C; that is to 

 say, they exei ted a force about twenty times at least as great 

 as the maximum force of a human muscle of the same thickness. 

 Still greater forces may be exerted by strips of cajutchouc 

 rendered in a high degree doubly refractive by strong extension. 

 Even by merely heating from 10' to 40" C. powers could be 

 produced sixty times as great as the maximum afTorJed by 

 human muscles of the same transverse section. 



Hence we may sufficiently account for the greatest display of 

 force in the muscle, without having to attribute to the inotag- 

 mata higher elastic forces than we observe in highly extended 

 threads of caoutchouc of the same thickness, nay, without even 

 having to assume temperatures reaching the degree necessary 

 for the coagulation of albumin. 



It is a pity that we are not al)le to subject the isolated doubly- 

 refractive parts of the muscle in an unimpaired condition to the 

 influence of heat. Together with the elevation of temperature 

 there occur changes in the chemical processes, an 1 therewith in 

 the material composition and mechanicil propertie;, of the 

 whole muscle substance, which complicate the change; de- 

 pendent only on the heating of the doably-refractive pirticle--, 

 or even prevent our clearly recognising I hem. 



Tclanus and Kigor by Heat. — Livmg muscles, when being 

 ^raJnal/y heated, will, as you know, contract tetanicilly sj 

 soon as the temperature has attained a height which ii but little 

 below 50' C. This so-called tetanus of heat passes b/ prolonged 

 heating into the lasting contraction of rigor, in this case 

 combined with definitive loss of irritability. 



This contraction through heat agrees at so many points with 

 physiological contraction, especially with physiological tetanu;, 

 that it w.as held to be a Jast manifestation of muscular life. 

 .Such points of resemblance are, e.g., the amount and the force 

 of shortening, which in bolh cases are at least of the same 

 order, and the increased production of heat, carbonic acid, and 

 a fixed acid. 



No doubt in this case a very important and general rise of 

 temperature of the contractile particles will take place so soon 

 as rigidity begins to announce itself. Consequently, according 

 to our hypothesis, we must expect a strong and general 

 contr.-iction of the inot.tgmata. 



That the force, with which the muscle as a whole will 

 shorten, is not quite so great as with physiological tetanus, is 

 sufficiently explained by the fact that the inotagmata d) not 

 contract simultaneously, and by the increase of internal re- 

 sistance which occurs, due to coagulation and precipitation in 

 the muscle plasma during the development of rigidity by heit. 

 The latter circumstance seems to explain, loo, why the rigid 

 muscle does not perceptibly lengthen, or lengthens very little, 

 upon cooling. 



Turgescence by Absorption as a General Cause of Contraction 

 <y Doubly. refractive Organised Elements. — On a closer examin- 

 .ition, however, we find that matters are still more complicated, 

 and likewise that there is still an important circumstance which, 

 besides the lise of temperature of inotagmata, may act as a 

 cause of contraction, even of permanent cjntraclion. This 

 circumstance, the fundamental importance of which to muscular 

 contraction was disclosed a score of years agd by a rigorous 

 microscopical examination of the processes taking place in the 



muscle fibres during contraction, is the turgescence of the doubly- 

 refractive elements by the absorption of watery liquids. 



All histological elements possessing doubly-refractive power 

 tend, even at an ordinary low temperature, to shorten in the 

 direction of the optical axis when their volume is enlarged by 

 the absorption of a watery fluid, and to lengthen when their 

 volume diminishes by loss of liquid. The extent, power, and 

 rapidily of the changes of form depend on the nature ond on the 

 dimensions of the turgescent object, and on the nature and 

 quantity of the absorbed liquid. 



For the examination of these relations our violin strings again 

 yield fit material. A long series of itieasurements has now 

 shown that there is a vety far-reaching resemblance between con- 

 traction by turgescence and thermal and physiological con- 

 traction. I may mention the marked extent of the shortening, 

 the high value of the force of contraction, its increase with the 

 initial tension and its decrease with incre.asing shortening, the 

 increase of extensibility, the decline of refractive power and of 

 doubly-refractive properly. The resemblance is by no means 

 exclusively of a qualitative, but also of a quantitative kind. 



A change of form generally takes place when the composition 

 of the absorbed liquid changes, and it is of great impoit.ance to 

 our question that even the slighte.t changes of composition can 

 cause marked contraclions and great mechanical effects. 



Unloaded E strings, e.g., contract in pure water to nine- 

 tenths, and in water which contains o 25 per cent, only of lactic 

 acid to three-fifths of the initial length. At 15' C. they exert, 

 in the first case, forces of about 80 g., in the second of about 

 nog. By absorbing a o"25 per cent, solution of lactic acid at 

 initial tensions of 5, 215, and 425 g. there were exerted powers 

 of "5> 35O' ^"fl 49° g- respectively, i.e. forces very much 

 higher than a muscle of the same thickness can produce during 

 teianus. 



Upon nentralisation or dilution the old length and volume 

 return. The doubly-refractive fibrils, or the sarcous elements 

 of muscles, contract considerably also under the same 

 conditions, swelling at the same time ; this is the case even 

 with muscles which have been killei in alcohol. In such 

 instances I measured in the striated fibres of insects shortenings 

 to 50 per cent, and more. 



Since, according to many inquirers, lactic acid is formed 



during the rigor of striated muscles, and at all events the 



reaction of the muscular plasma becomes acid, the dcubly- 



I refractive elements must necessarily swell more and tend to 



I shorten, and this contraction will remain uaiil the acid has been 



' neutralised or removed by diffusion. 



Similar results will follow in other cases of rigor characterised 

 by shortening and by the production of much acid. X.ay, in 

 the bloodless muscle even a physiological stimulation, when 

 sufficiently strong an<l long, may be expected to produce a 

 lasting shortening, on account of the gradual increasing acidity. 

 Indeed, the well-known incomplete relaxation of such muscles 

 seems to me to be a symptom of this chemical contraction, as it 

 may be called, in contrast with the thermal. 



In a muscle in which the blood stream is maintained this will 

 not so easily take place, not even under a strong and prolonged 

 stimulation, because the acid is immediately neutralised or re- 

 moved through diffusion. Even in the isolated, bloodless 

 muscle ihe acid, which is produced by stimulalion, may, in the 

 beginning at least, be tendered harmless through the very large 

 quaniity of non-acid fluid absorbed by the muscle. Conse- 

 quently we must expect in these cases an immediate and com- 

 plete relaxation after contraction. The facts agree absolutely 

 with these suppositions. 



It is, perhaps, not unnecessary to remark that all these obser- 

 vations would also hold good if the material affecting the tur- 

 gescence were not lactic acid, but another substance aiising 

 during the chemical action in I he mu«cle, e.g. water. 



The different parts played by " riurmal " and by ' ' Chemical" 

 Contraction in the different kinds of Muscular Contraction. — 

 But now the question may be raised, Is not physiological con- 

 traction due to turgescence solely ? 



\Vc have all the more reason to put this question, since we 

 can prove that in the physiological contraction of siriated 

 muscle-fibres the doubly-refractive layers swell at the cost of 

 the watery isotropic layers. The micioscopic.al examination of 

 active living musclts and of fixed waves of contraction has 

 proved this fact beyond all question, however much the opinicns 

 of different observers may diverge on other points. The swell- 



NO. 1326, VOL. 51] 



