THE PROPERTIES OF STRIPED MUSCLE. 



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 

 - 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, have already called " inertia 

 the heavy lever described on p. 360 being used -n 4. i 



T..-.L __ A J __._VA-J 77, ! -i ' .,, curves. By taking the ac- 



but not weighted; bV, similar curves Avith 

 the lever weighted on either side of the axis 

 with 500 grms. After Schenck. 



companying 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, 



FIG. 202.--Schenck's apparatus for taking this could be done at any desired 

 "jerk curves." L, isotonic lever : HH', period, and it was found that if 

 light wooden lever, working on the axle done at the very beginning of an 

 A, with one arm attached to lower end of i so tomc contraction, the jerk scarcely 



rrft3*^^&J*2? affected th <\ time , of . r f axatio " 



held down by the electro-magnet R, and ( Fl g- 203 > A ) ', for tne J erk curve 



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



Schenck. j n fais 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. 



L*. 



