388 MUSCULAR ACTION 



the senses. It remains here to look at this muscular coordination and 

 control mostly from the side of the muscles. (See Fig. 188, p. 334.) 



It has been emphasized that the nerves form with the muscles (and 

 glands and sense-organs) a functional unity if not a complete structural 

 continuum of protoplasm, a principle of importance in the theory of 

 muscular control. Philosophically one has to consider the nerve- 

 muscle group of organs as agent of the individual will ready at all times 

 to bring about whatever movement the biological needs of the animal 

 demand. It is only by the intimate union of the nervous system with the 

 muscle system, reaching thereby nearly every body-cell, that the muscles 

 are made almost the universal instrument of every function in one way 

 and degree or another. In other words, the all-pervading " nerve-net" 

 brings, perhaps, into the immediate service of every part of the body 

 practically the whole muscle-mechanism. 



The relations of voluntary movement to reflex movement were dis- 

 cussed in the chapter on the Nervous System. It is largely a matter of 

 habit, of repetition until the action is on a mechanical basis almost, that 

 finally turns a laborious new voluntary movement, made only at first by 

 exercise of perhaps strained attention, into a reflex group of movements 

 nearly free of mental effort. The muscles in unity with the nerve-net 

 learn, acquire readiness and coordinated accuracy, what, in short, is 

 known as skill or, more broadly looking, cleverness. What is the mus- 

 cular side of the development of this capacity, one of the most precious 

 of man's powers, one of the largest elements in the evolution of his 

 civilization and culture ? While, indeed, " the reign of the brain is plain/' 

 it is easy to limit too closely what we mean by " brain" and to forget that 

 the nervous system is above all a system of conducting paths. These are 

 so infinitely devious that in a sense they form a net, and yet they are 

 useless without something to connect, without some way of expressing 

 in the material, practical world that system of adjustments which com- 

 bined are life. The most immediate agent in this direction is the mus- 

 cular system. How then does a musculature learn? and in learning, 

 what development does it undergo ? 



There are two directions in which a muscle may develop: vigor and 

 strength, and skill or delicacy of adjustment. The latter, skill, involves 

 a degree of the former, vigor, but, on the other hand, the vigor may be 

 present with little delicacy of coordination. To some extent, indeed, in 

 their higher degrees these are opposed and in practice rarely present in 

 the same muscle-group. The strong-man in the circus is seldom a grace- 

 ful dancer, and the expert engraver or musician is only rarely an athlete. 

 The reason for this lies largely in the fact that the time required for one 

 sort of development excludes development of the other kind; but there is 

 a true physiological opposition of a certain degree. In athletic training 

 the endeavor is constantly to overcome this opposition, to acquire skill 

 in playing combined with a large degree of strength. The games in 

 which both mean much, such as tennis, golf, rowing, or base-ball, are 

 then theoretically the best for the general good of the organism. 



