Force Brown- S^quard. 



15 



labor; if \vo spend force with the pen in hand, when wo 

 urc studying quietly at a table, we find, after having 

 tieon at work three or four or five hours, tluit tlie nerve 

 force that remains for physical exercise is 

 diminished. Wo have drawn force from a focus 

 which is the same that gives it for mental 

 action and for physical exertion. If, on 



the other hand, we walk 30 miles and find ourselves 

 physically tiied.we find then that very little nerve force 

 remains for mental action. Tliere are facts, however, 

 which seem to lie in opposition to this, and those facts 

 will be fully explained in the last lecture, when I conio 

 to explain the laws of production and expenditure of 

 nervous force. I may say this much, ho vever, just here, 

 that it is perfectly well known, contrary to what I have 

 said, that we can do better with our brain if 

 we have had some exercise than if we 

 have had no exercise at all. But it is 

 simply that a certain amount of exercise 

 has led lo the production of nervous force liy improving 

 the circulation, improving the secretions, improving 

 respiration, and improving in fact all the great organic 

 functions through which the secretion of nervous force 

 takes place, so that we have become richer in our force 

 because of the exercise we have taken physically. There 

 is no doubt, therefore, that moderate exercise will lead 

 to a production of nerve force and facilitate the exercise 

 of our > i ram power; and there is no question that if 

 we draw too much of the nerve force of our system, if 

 we draw a great deal more of it than can he re- 

 produced during a certain time; if we walk, 

 for instant, very fast for five or six hours, 

 "KG Off then unfilled for mental work 

 and for a good many other things. Our respiration be- 

 comes difficult. Our heart, after bavins beaten with 

 much rapidity, comes to bea;; very slowly. We are 

 weakened in every organ whose action depends on ner- 

 vous force. There is no doubt therefore that there is a 

 common focus of nerve force on which we draw for any 

 of the activities of our system employing nerve force. 

 Looking through a microscope for several hours, as mi- 

 crographers know full well, is a cause of great fatigue, 

 and renders mental work or physical labor thereaf- 

 ter more difficult. 



THE I'NITY OF NERVOUS JORCE. 



There is one experiment that shows tUat nerve force 

 is distributed as galvanism would be on a cylinder. 

 Suppose a cylinder in the shape of my arm; suppose 

 that this is charged with a certain amount of elec- 

 tricity, and suppose that this arm or cylinder is then 

 cut in two. just in the middle of its length ; there would 

 be in eacn half of the arm then an amount of elec- 

 tricity which would lie just one-half of tl.o amount 

 that existed before. Suppose that the whole 

 arm had manifested a force equal to twenty measures, 

 the half of the arm would manifest a force equal to ten. 

 So it seems to be with the nervons system. If we di- 

 vide the cord across, as in a bird, behind the upper limbs, 

 we find that the bird cannot make use of its limbs 

 &e before. The amount, of force is not sufficient in the 

 upper part of the nervous system. So it seems that 

 nervous force is distributed all over the nervous system, 

 and that if a cause, operates to divide the nervous sys- 

 tem into halves, each half has only the amount of nerve 

 force which it had before. 



There is one objection in appearance to tl>2 view that 

 there is unity of nerve force, ra4 that is that the, brain 

 Is a double organ ; that we have two brains instead of 

 one. About that allow me to say that although we have 

 two brains it Is pretty much as if we had but one, as by 



the force of our education one only Is raised to power 

 The other is left with very little, power indeed. It would 

 be very easy, as I may hereafter show, to develop fully 

 the power of the two brains by proper educ.ition. But 

 if we have two brains there is no objection to the view 

 that there is a unity for the nervous force. It is no ob- 

 jection because these two brain.* are united. 

 There is communication. Every part of our 

 nervous system is In communication with the 

 other. Wo cannot touch a part of the skin 

 or any other part of our system without producing a 

 commotion all over the nervous system; in the same 

 way that we cannot stamp our foot on the ground with- 

 out shaking the whole world, and not only our world 

 but the rest of the universe is shaker, by such a simple 

 thing as that. Of course, a very little shaken [laughter |, 

 but shaken nevertheless. There is no doubt that any 

 action on any port of our system is felt everywhere 

 through it. And that is tho reason why many persons 

 suffering in their nervous system cannot have an excita- 

 tion brought on any part of the body, as It increases the 

 trouble where it exists. 



A few questions remain to be examined before 'closing 

 the. lecture. One is, how happens it that there are so 

 many ditt'ereuces in sensation if there be but one kind 

 of nerve force. This is not a great difficulty. The va- 

 riety of sensations has an organic cause, oi which I may 

 have an opportunity to speak in another lecture. The 

 nerve force is only an agent, most likely the vibration of 

 a certain aaent, and the vibration according to the loca- 

 tion will produce one efiect or another. The parts of 

 the nervous system are not all alike; they certainly dif- 

 fer one from another, and the vibrations may be greater 

 or less, so that we can easily be reconciled to the va- 

 riety of sensation, although we admit but one kind of 

 nerve power. 



There is another question. That certain fibers seem to 

 act on muscles, and others seem to restrain tho nervous 

 action. This is a point of such great importance that I 

 shall give a whole lecture to that subject. When cells 

 are active, either morbidly or naturally, an irritation 

 coming from a nerve and acting certainly through nerve 

 forces may be sufficient to stop the power of that nerve 

 cell. That seems to be an act completely different from 

 that by which a muscle, for instance, is put in action by 

 the vibrations taking placa; the transformations of 

 nerve force taking place in the nerve, and also all 

 the other actions that I spoke of the emission of light 

 and electricity. All these things may seam to imply 

 some different action. But if you admit the groat doc- 

 trine which exists now in science, and which has revo- 

 lutionized natural philosophy as well as chemistry; if 

 you admit that there is never a loss of force; that force 

 is accumulated and that it is only transformed when it 

 disappears, then you can easily admit that nerve force 

 has been transformed in those various organs into 

 some other force ami that there lies the 

 cause of the different actions <( winch I 

 have spoken. But tho difficulty exists, how- 

 ever, for that special case in which au action ceases m 

 the cell. Suppose a person to have an attack of epilepsy. 

 Hia head is thrown to one shoulder and he has not yet 

 lost consciousness, and some one comes and draws the 

 head to the other shoulder and the fit ceases. Well, 

 there has been in that case an irritation starting from 

 certain nerves when the head was moved, and this irri- 

 tation goes to the cells of tho gray matter that were 

 active in producing the convulsions find stops the 

 action of those cells. But the stopping of tho action of 

 cells is something different from the production of ao- 



