64 Proceedings of Royal Society of Edinburgh. [sess. 
with four corresponding binding screws below the instrument; 
thus all necessary connections can be easily made even when the 
upper part is covered by a glass moist chamber. The instrument is 
supported by a strong brass bracket which can be firmly clamped 
on the stand by means of a screw (N), and is also provided with 
coarse and fine (R) adjustments for inclining it at a convenient 
angle. 
B. Uses. 
1. The chief purpose for which the instrument was designed 
was to obtain a method of graphic representation of the character 
and velocity of the contraction of frog’s muscle immediately 
following an absolutely isometric stimulation. If a muscle is 
stimulated — say electrically — in the ordinary course of events, it 
contracts. But when a muscle is prevented from shortening 
during stimulation it undergoes a change of tension. This change 
of tension while the length of the muscle remains unaltered has 
been designated by Fick* as isometric condition. In my instrument 
a simple contrivance has been made for the rapid contraction of a 
muscle immediately after its tension is raised under absolute 
isometric condition, or in other words, by means of single induction 
shocks I have produced in frog’s muscle a condition resembling 
what in the case of rapid voluntary contraction, has been called by 
Hay craft f “ hold and let go ” method. 
For this purpose a nerve-muscle preparation of frog’s gastro- 
cnemius is supported horizontally, its femoral end being firmly 
clamped and the tendo Achillis fixed to the lever by means of a 
hook as indicated in fig. 2. On the other side of the pivot the 
lever is held by means of a very thin elastic band (0) clamped at 
one end like the muscle and attached to the lever at the other. 
Although the elastic band is able to hold the lever in position, 
keeping, on the other side, the muscle suspended without any 
laxity, it has only a small amount of initial tension ; so that even 
when it is fully extended, due to the movement of the lever during 
contraction of the muscle, the elastic tension of the band does not 
* Arbeitleistung und Warmeentwickelung lei der Muskelthatigkeit. Leipzig, 
1882, S. 131 ; also Pfltiger’s Archiv , Band xlv. p. 297. 
f Journal of Physiology , vol. xxiii. Nos. 1 and 2. 
