1907.] on Nerve as a Master of Muscle. Gil 



during which it pays no attention to the further stimulation, and 

 relaxes ; and only after it has fully relaxed does it again pay atten- 

 tion to the stimulus and contract, that it to say, beat again. In 

 short, it replies rhythmically to a continued stimulus which would keep 

 the other muscle continuously contracted. 



That the heart should go on beating after removal from the 

 body, does not seem greatly surprising because it is still then alive. 

 The wonder lies rather in its continuing to live so long when thus 

 removed : that granted, it seems natural that it should do what it 

 has done previously all its life. 



But this other muscle, which likewise continues to live when re- 

 moved from the body ; it, though it can contract, does not. That 

 seems — at least at first sight — the more remarkable. Why does this 

 muscle stop ? So long as it was part of the living creature it showed 

 contraction over and over again. We must turn to the nervous 

 system for our answer. 



In the first place let us note that an animal, unlike that other great 

 example of life, a plant, cannot nourish itself from naked earth and 

 air alone. The plant strikes down roots and throws up leaves, and 

 draws through these material and energy with which it can replenish 

 its own substance and activities. Where it as a seed fell, there its 

 foster-mother Earth gives it the food it wants. Not so the animal. 

 It must have subtler and rarer stuffs, or die. The material it needs is 

 not spread so broadcast. It, to replenish itself, must have more 

 special material : it must have for food material that is living, or has 

 lived. To obtain this it has to range about. It has to hunt for it. 

 And it itself is hunted by other animals following the same quest. 

 Therefore its very existence involves locomotion. It must find food 

 and seize it, and must itself escape being found and seized. It is 

 both hunter and hunted. Moreover in a vast number of cases it has 

 to seek its kind, to propagate its species. The movement necessaiy 

 in this great game of life is million-sided — subtle beyond words — and 

 most animal lives are spent in nothing else. Existence for tha 

 individual and the race depends upon success in it. Man plays it also 

 — let us hope that sometimes he plays something else as well. In all 

 cases the chief instruments of the game are the skeletal muscles, 

 those muscles of which the biceps of our arm may stand as type. 

 An old philosophic adage has it that all which mankind can effect 

 is to move things. The dictum illustrates how supremely chief an 

 executant of man's activity his muscles are. And all the things which 

 man can move are moved in the first instance by that prime thing 

 which he can move, his body. And for this his main agents are his 

 skeletal muscles. These execute his movements, but in doing so 

 are but the instruments of his nervous system. Therefore it is 

 in reality the nervous system which is the player of the game. And 

 it is because it is really the nervous system which is the player of the 

 game that man is the most successful creature on earth's surface at the 



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