1899-1900.] Mr Mahalanobis on a New Form of Myograph. 67 
the muscle can be varied. The amount of tension at different 
stages of contraction of the muscle can he estimated by noting the 
extent of deviation of the writing point from the abscissa produced 
by known weights placed on a scale-pan suspended below the 
instrument by a string tied to the muscle hook and passed over the 
pulley (P). 
The pulley can be similarly utilised in experiments on elasticity 
and extension of muscle, etc. Then besides most of the common 
experiments on the physiology of muscle, e.g ., fatigue, tetanus, 
etc., the instrument can with some manipulation he used to 
illustrate the action of antagonistic muscles by using a pair of 
gastrocnemii of the frog. 
C. Advantages. 
It seems to me that, apart from the special use of the apparatus, 
this form of myograph, with horizontal movements of the lever, 
has some advantage over the usual form where the lever moves in 
a more or less vertical manner. In the first place, here the 
influence of gravity on the movements of the lever is nil. 
Besides, in the case of vertically moving levers we find that, even 
when the lever is very light and the weight attached to it is small, 
the lever, owing to its mass and moving with great rapidity, gathers 
momentum : in virtue of which not only the lever tends to move 
upwards even when the contraction of the muscle has stopped, hut 
also the tension of the muscle is diminished, thus seriously inter- 
fering with the isotonic condition of the latter. The same thing 
happens in the opposite direction during the downward excursion 
of the lever, i.e., it continues to pull down the muscle beyond its 
initial extension. Thus the so-called isotonic curve is rendered 
untrustworthy, as has been strenuously urged by Kaiser.* 
In a horizontally moving lever, where a very thin elastic hand is 
used, and the point of its attachment is close to the fulcrum, the 
slight increase of tension of the elastic band, due to its extension 
during the contraction of the muscle, tends to neutralise the 
influence of the momentum of the lever. 
Zeitschr. f. Biol . , vol. 33. 
