428 Prof. Th. W. Engelmami. [Mar. 14, 



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

 rature 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 contraction of the inotagmata. 



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 do not contract simul- 

 taneously, and by the increase of internal resistance which occurs, due 

 to coagulation and precipitation in the muscle plasma during the 

 development of rigidity by heat. The latter circumstance seems to 

 explain, too, why the rigid muscle does not perceptibly, or only very 

 little, lengthen upon cooling. 



Turgescence by Imbibition as a General Cause of Contraction of 

 Doubly-refractive Organised Elements. On a closer examination, how- 

 ever, we find that matters are still more complicated, and likewise 

 that there is still an important circumstance which, besides the rise of 

 temperature of inotagmata, may act as a cause of contraction, even 

 of permanent contraction. This circumstance, the fundamental 

 importance of which to muscular contraction was disclosed a score of 

 years ago 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 imbibition of watery liquids. 



All histologicai elements possessing doubly-refractive power tend, 

 even at an ordinary low temperature, to contract in the direction of 

 the optical axis when their volume is enlarged by the imbibition of a 

 watery fluid, and to lengthen when their volume diminishes by loss 

 of liquid. The extent, power, and rapidity of the changes of form 

 depend on the nature and on the dimensions of the turgescent object, 

 and on the nature and quantity of the imbibed liquid. 



For the examination of these relations our violin strings again 

 yield fit material. A long series of measurements has now shown 

 that there is a very close resemblance between contraction by im- 

 bibition and thermal and physiological contraction. 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 

 increasing shortening, the increase of extensibility, the decline of 

 refractive power and of doubly-refractive property. 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 imbibed liquid changes, and it is of great importance to our 

 question that even the slightest changes of composition can cause 

 marked contractions and great mechanical effects. 



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

 in water which contains 0'25 per cent, only of lactic acid to three- 



