346 MOTION TN ANIMALS AND PLANTS. 



about a tenth of a second (during which a quasi psychological process 

 is going on in the spinal cord) the muscle responds. A curve is drawn 

 simultaneously by the writing lever to which the end of the muscle is 

 attached, which indicates that it is in spasm ;^ but it is the photo- 

 graphic curve which tells us the nature of that spasm. Each ascent of 

 the meniscus is seen to be the response, not to a single instantaneous, 

 but to a short continuous, stimulation, of which the duration can be 

 easily deduced l)v measuring the time interval between the beginning 

 and the culmination of an excursion. By subjecting the muscle arti- 

 ficially to series of excitations of similar duration with corresponding 

 intervals of inactivity one can produce an imitation of the strychnine 

 spasm which, both in its mechanical and electrical characters, resembles 

 the natural one. (See photograph 7.) 



Before leaving the subject of the strychnine reflex I must refer 

 very briefly to such previous observations as bear on our present 

 inquiry. The phenomenon is of interest as being one which could 

 not have been discovered had we not possessed the capillary electrom- 

 eter. Its discovery was, indeed, the outcome of the first attempt 

 made by Prof. C. Loven to use that instrument for tlie investigation 

 of the electrical properties of muscle just twenty years ago. He was 

 good enough to make for me the electrometer which was used in some 

 of my own earliest experiments. Shortly afterwards Mr. Page 

 devised the method of obtaining photographic records of our own 

 results and, amongst others, of those of Loven relating to the strych- 

 nine spasm. Loven's observation has served ever since as a support 

 for the doctrine of discontinuity. No one would be more willing than 

 he would, if he were with us this afternoon, to recognize its true 

 meaning. 



The conclusion to which all the facts we have had before us up to 

 this moment lead is that normal muscular action is the manifestation 

 of what happens in the motor nervous system. If this motor impulse 

 is so short that we are obliged to call it "instantaneous," the response 

 is correspondingly brief; if it lasts longer, we call it "continuous," 

 recognizing that the difi'erence between the two is merely one of 

 duration. In either case it is of the essence of the response that it 

 is terminable. There is no difiiculty in understanding on teleological 

 grounds why a muscle must relax; but of the mechanism by which it 

 is brought about we know little, excepting that it is localized in the 

 muscular structure. Each element— each tagma— returns to its status 

 quo in the same way in a curarized muscle as in a normal one; but 

 whether this power of recovery is a process by itself, as some physi- 

 ologists hold, is a question which is at this moment debated, but by no 

 means settled. It is only in so far as it relates to the electrical con- 



1 The curve is often toothed, the teeth corresponding in frequency with the elec- 

 trical undulations. 



