37° 



THE PROPERTIES OF STRIPED MUSCLE. 



the lever weighted on either side of the axis 

 with 500 grins. — After Schenck. 



which it eventually attains, and that this position is different in relation 

 to the former in a cooled muscle from what it is in one that has been 

 warmed. It will be seen later, that in this observation he is comparing 

 •very different stages in the progress of a muscle from the unexcited to 

 the excited condition. 



Similar considerations led Schenck to investigate the effect of different 

 kinds of augmentation of tension, having regard especially to its amount, 



rapidity of development, and 



A ^ ^= — duration. He experimented 



first with the equilibrated 



oscillating bar, coupled with 



the isotonic lever, in a similar 



way to that used by Fick 



(p. 359), thus obtaining Schleu- 



derzuckungen, the curves of 



Fig. 201. — m, Normal isometric curve ; t, normal which (as shown in Fig. 193, 



isotonic curve of the same muscle ; a a', inertia or in Fig. 201, B) are what I 



curves of tension and shortening respectively, naV e already called "inertia 



the heavy lever described on p 360 being used curveS- » By taking the ac- 



but not weighted ; b b , similar curves with . J . . ° 



companymg tension - curves, 



he shows (Fig. 201, A) that 

 whether the contraction of the 

 muscle is delayed by the inertia of the bar before the commencement of 

 shortening, or later, so long as the increase of tension ceases during the first 



half of the period of contraction, as 

 happens when the bar is unloaded, 

 the fall of the curve of shortening 

 a, is either in front of, or almost 

 coincides with, that of the isotonic 

 curve t. If, however, the moment 



■/?) of inertia of the bar is augmented by 



weighting its ends, so that the aug- 



□ mentation of tension lasts much 



longer (curve b), the maximum of 

 contraction is reached later, and the 

 fall of the curve is beyond what it 

 would have been in the absence of 

 the bar. 



He subsequently experimented 

 with more sudden and transient aug- 

 mentations of tension by jerking the 

 writing-lever downwards during an 

 isotonic contraction. 1 By an ingeni- 

 ous contrivance, shown in Fig. 202, 

 this could be done at any desired 

 period, and it was found that if 

 done at the very beginning of an 



A" 



202.-— Schenck's apparatus for taking 



'jerk curves." L, isotonic lever ; H H', 



light wooden lever, working on the axle 



A, with one aim attached to lower end of i so t nic contraction, the jerk scarcely 

 muscle and isotonic lever by the thread «. , ■, .i ,• V „^ ava ^ n „ 



nk; F, spring fixed at B, which can be aff ected the time of _ relaxation 

 held down by the electro-magnet E., and (Fig. 203, A) ; for the jerk curve 

 which, when let go, strikes H'.— After (as I propose to call curves produced 

 Schenck. - n ^g way ) coincided in its decline 



with the isotonic curve. The later the jerk took place, the sooner the 

 relaxation of the muscle occurred (Fig. 203, B). The contrast between the 



1 Schenck, Arch. f. d. yes. Physiol., Bonn, 1895, Bd. Ixi. S. 77. 



