258 THE ADRENAL SYSTEM AND VASOMOTOR FUNCTIONS. 



uations in what, for the sake of convenience, we may call 

 "intensity." The impulse-wave simply sets the muscle-elements 

 to a given vibratory rhythm, and they retain this, whatever 

 be the intensity of the exertion required. The oxidation proc- 

 ess, on the contrary, contributes whatever degree of mechan- 

 ical energy is necessary to fulfill the needs, not only of the 

 movement, but also of any additional work an increase of 

 resistance may demand. Thus, the impulse-wave may fix the 

 muscles of the flexed arm in a given position, but any fluctua- 

 tion in the power required to support different weights is at 

 the expense of the motor mechanism. This may be aptly 

 compared to the manner in which a note on a violin is made 

 loud or soft. The power with which the string is pressed upon 

 with the moving bow modifies the intensity of the sound; but 

 the note remains the same. This means that its pitch does 

 not vary, and if, for example, the lower C is given, we will 

 know that the sound-wave of that note represents 261 vibra- 

 tions per second. So may the impulse-wave transmitted by the 

 brain through a "motor" nerve be represented by a fixed num- 

 ber of vibrations. Retraction, the muscle being then most 

 tense, is therefore characterized by the greatest number of 

 vibrations. On receiving the impulse the muscle adjusts itself, 

 whether by contraction or retraction, to precisely the extent 

 which the number of vibrations transmitted will allow, and 

 remains fixed in the state of contractility assumed until the 

 impulse-wave itself is modified. The power or intensity of 

 sound and the variations in the work this implies are fully 

 typified by the motor process, through the enhanced circula- 

 tory activity and a corresponding increase in the rapidity with 

 which the oxidizing substance is brought into contact with 

 the myosinogen in the muscles. It is simply a question here 

 of more fuel and more draught. 



Obviously, the rhythm transmitted to a voluntary muscle 

 is simultaneously communicated to the muscular walls of its 

 vessels by the same impulse. The lumen of each vessel veins 

 as well as arteries, since the former also possess a muscular 

 coat, but much less important structurally and therefore less 

 active varying synchronously with the muscle to which it is 

 distributed, the flow of blood through it is exactly adjusted 



