THE MECHANICAL RESPONSE. 



365 



the parent of many other contrivances for the same purpose. It consists of a 

 light lever h /?/, round the axis of which, a, runs a pliable but inextensible 

 thread with a hook at its free end, c, which is attached to the lever H H' 

 previously described, at the same point d at which the muscle is attached ; 

 connected with the lever hti by a stiff wire is a rigid bar, //', fixed at /. 



FIG. 195. Blix's apparatus for recording isometric and isotonic curves synchronically. 

 p, the support ; 1 1', isometric lever ; I, isotonic lever ; x and y, wires from the 

 secondary coil of an inductorium. The muscle occupies the position indicated by 

 the broken line. For taking an isometric curve, the lever Z and the attachment 

 of the muscle to it, are made immovable by means of the clamp, Cl. When the 

 clamp is open, I records an isotonic curve. Its movement is resisted by a weight, 

 the thread supporting which is wound round the axle. A screw serves to adjust 

 the isometric lever in the way shown in Fig. 1 95A. 



When the muscle is excited it strives to 

 rotate the axis a, but is opposed in this 

 effort by the steel spring //'. The ten- 

 sion it acquires is recorded graphically by 

 a writer s. If during the existence of 

 this tension the hook c is unhitched from 

 its pin d, the excited muscle at once 

 shortens to the length which it possesses 

 when left to itself. This shortening can 

 also be recorded by a writer s', on the 

 lever H H'. 



Fick's first purpose was to register the 

 changes of tension in a muscle striving 

 to contract, but entirely prevented from 

 doing so. Subsequently, the method was 

 extended to the case in which a muscle 

 contracts against resistance, and instru- 

 ments were contrived by which tension 

 and shortening could be recorded simul- 

 taneously. Although Fick's original myotonograph gave curves which exhibit 

 to a considerable extent the deformation which arises from friction and 

 inertia, the records obtained by the more perfect tension- writer of his pupils 

 Schonlein and Schenck are not open to this objection. 1 



1 Schenck, Arch.f. d. ges. Physiol., Bonn, 1892, Bd. lii. S. 108. 



, 195A. Enlarged view of the same 

 apparatus, to show the torsion rod 

 from above. 



