1907.] Nerve as a Master of Muscle. 609 



WEEKLY EVENING MEETING, 



Friday, April 19, 1907. 



The Right Hon. Earl Cathcart, D.L. J. P., Manager, 

 in the Chair. 



Professor C. S. Sherrington, M.A. M.D. LL.D. D.Sc. F.R.S. 



Nerve as a Master of Muscle. 



We have on the table before us two muscles. The animal was dead 

 when they were taken from it a short while ago. But the animal 

 was, as we are ourselves, an assemblage of organs, and many of these 

 organs go on living for a certain time after the animal, as an animal, 

 is dead. Hence these muscles, carefully removed, are still ahve. 

 We notice a marked difference between their behaviour now. To 

 understand the behaviour of organisms we have to think of them as 

 processes rather than as structures. An animal is something hap- 

 pening. The function of muscles is to contract. Of the two muscles 

 now before us, one still goes on contracting, although quite isolated 

 from the body of which it formed a part ; but the other does not 

 contract, although that is its function in the body. The muscle 

 which still goes on contracting is the heart ; the other is a muscle 

 hke the biceps of our own arm. We might think that, as it rests 

 there motionless, it is not alive. It is, however, fully alive. We can 

 satisfy ourselves of that. If I apply to it a faint electric current, 

 it answers by exhibiting its functional activity — it contracts. Yet 

 it does not contract of itself, nor will it, however long we may 

 preserve it ; it will die without of itself even contracting once. 

 What is the significance of this difference between the two ? 



The secret of this difference is largely an affair of the nervous 

 system. The tie between muscular activity and nervous activity is 

 always close ; but it is very different in different muscles. The 

 nervous system has been called, with a picturesque truth, the master- 

 system of the body. It controls the action of organs ; it controls, 

 quite especially, the activity of the muscles. This heart which we 

 see beating here receives nerves. One of those nerves when stimu- 

 lated will cause it to contract less, the other to contract more. The 

 contraction of the heart is its " beat." The vagus nerve slows the 

 beating, the other nerve quickens the beating. 



The heart is a tubular muscle ; it drives blood through itself. 

 When it contracts it squeezes the blood from it into the arteries, and 

 so the blood flows to feed all the myriads of minute Lives — cells — 

 Vol. XYIII. (No. 101) 2 r 



