THE MECHANICAL RESPONSE. 



365 



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

 light lever h 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 /. 



■w 



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 I and the attachment 

 of the muscle to it, are made immovable by means of the clamp, CI. 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. 195a. 



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 HH'. 



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. yes. Physiol., Bonn, 1892, Bd. Hi. S. 108. 



Fig. 195a. — Enlarged view of the same 

 apparatus, to show the torsion rod 

 from above. 



