CHAP, ii.] 



THE CONTRACTILE TISSUES. 



43 



FIG. 2. The muscle-nerve preparation of Fig. 1, with the clamp, electrodes, and 

 electrode-holder, are here shewn on a larger scale. The letters as in Fig. 1. 



The apparatus figured in Figs. 1 and 2 is intended merely to illustrate the general 

 method of studying muscular contraction; it is not to be supposed that the 

 details here given are universally adopted or indeed the best for all purposes. 



lever will by its movement indicate the extent and duration of the 

 shortening. If the point of the lever be brought to bear on some 

 rapidly travelling surface, on which it leaves a mark (being for this 

 purpose armed with a pen and ink if the surface be plain paper, or 

 with a bristle or needle if the surface be smoked glass or paper), so 

 long as the muscle remains at rest the lever will describe an even 

 line. When, however, a contraction takes place, as when a single 

 induction-shock is sent through the nerve, some such curve as that 

 shewn in Fig. 3 will be described, the lever rising with the shorten- 



Fio. 3. 



A MUSCLE- CURVE OBTAINED BY MEANS OF THE PENDULUM MTOQRAPH. 

 To be read from left to right. 



6 the 



a indicates the moment at which the induction- shock is sent into the nerve. 



commencement, c the maximum, and d the close of the contraction. 

 Below the muscle-curve is the curve drawn by a tuning-fork making 180 double 

 vibrations a second, each complete curve representing therefore ^rv f a second. 

 It will be observed that the plate of the myograph was travelling more rapidly 

 towards the close than at the beginning of the contraction, as shewn by the greater 

 length of the vibration- curves. 



ing of the muscle, and descending as the muscle returns to its natural 

 length. This is known as the ' muscle-curve.' In order to make 

 the ' muscle-curve ' complete, it is necessary to mark on the record- 

 ing surface the exact time at which the induction-shock is sent 

 into the nerve, and also to note the speed at which the recording 

 surface is travelling. These points are best effected by means of 

 the pendulum myograph, Fig. 4. 



In this instrument a smoked glass plate, on which a lever writes, forms 

 the bob of a pendulum and consequently swings with it. The pendulum 

 with the glass plate attached being raised up, is suddenly let go. It swings 

 of course to the opposite side, the glass plate travels through an arc of a 

 circle, and, the lever being stationary, the point of the lever describes an 

 arc on the glass plate. The rate at which the glass plate travels, i.e. the 

 time it takes for the lever-point to describe a line of a given length on 



