NERVES AND NERVOUSNES 



By DA\"ID FRASER HARRIS, M.D., B.Sc. (LOND.) 

 ^Lecturer on Pliysiulogy, Ciiii'crsify of rUnii iir^hitiii .) 



Possibly no terms are so looseh' used as " nerves," 

 and " nervousness." Owing to the prevailing ignor- 

 ance about the nervous svstem the\' have become of 

 much profit to the quack and the charlatan. Before 

 we attempt to understand in what " ner%'()usness " 

 consists, and wh\' some people are '" nervous "' and 

 others not. we should find out what a nervous system 

 does, what the possession of it means, and what would 

 be the result of our not having one. The central 

 nervous s\-stem is a mass of very highly specialised 

 living matter (nerve-cells) contained inside the skull 

 and spinal column in order to be protected from 

 injurN' from outside. Into and out of this mass of 

 nerve-cells run certain nerves from and to the 

 " peripherv," b\' which we mean all the b(>d\' 

 exclusive of the central nervous s\stem itself. Most 

 of the nerves going in, carr\- impulses which arouse 

 sensations, most of the nerves going out, carrv out 

 impulses which arouse movement : by the former 

 the environment acts on us. bv the latter we act on 

 the environment. The nervous s\stem as a whole 

 is the great means of communication between one 

 part of the body and another : without it we should 

 be totallv unaware of what was going on around us. 

 We should have no sensations and no pain : 

 although possessing eyes we should not see, though 

 having ears we should not hear : and, not ha\ing 

 an\- sensations, we should have no emotions and no 

 ideas, since these are higher mental states com- 

 pounded of the more fundamental states of sensation 

 and perception. Of course we should have no 

 memorv, as there would be nothing to remember. 

 Again, if we had no nervous system, we should not 

 be able to move a muscle when we wished ; no 

 matter in what danger we found ourselves we should 

 be powerless to escape from it. One part of the 

 bodv would not have the least idea where the other 

 part was. what it was doing, or what it wanted : we 

 should have no knowledge of the world around us or 

 of our relationship to it. We could initiate no 

 bodily activit\% and so would be powerless to make 

 any change whatever in the relations between the 

 environment and nursehes. lUit b\ means of the 

 afferent nerves the centres do receive information 

 regarding both the body and the outside world, and. 

 in consequence, the individual, through his centres 

 and efferent nerves, can constantly adjust his liody to 

 the changing conditions of the environment. 



The management of an armv is a good analogy 

 with the working of the nervous svstem. The army 

 council — a few men — we ma\- liken to the highest 

 parts of the brain, the intelligence department and 

 signallers to the afferent nerves, the rank and file of 

 the soldiers to the muscles — tht- ultimate executants 



of the orders issued by the council. >'ow the 

 soldiers, left to themsel\-es, w ould never of themselves 

 engage in any plan of concerted action. They !nust 

 be drilled, made to execute first independent and 

 then corporate movements in accordance with 

 definite orders, the meaning of which the}' have 

 previously learned. The men must be arranged in 

 squads, companies, regiments and battalions, and 

 must go through manoeuvres from time to time to 

 practise what would be required of them in actual 

 warfare. But in order that the army council issue 

 appropriate commands, it must be kept informed as 

 to the condition, number and distribution of all the 

 units constituting the army. The soldiers are the 

 muscles : if left to themseh'es, that is not attended 

 to b\- the central ner\-ous system, the}- might act 

 spontaneously from time to time, but not alwa\-s in 

 a manner calculated to promote the well-being of 

 the organism as a whole of which they form the 

 constituent parts. The luen must be drilled by 

 sergeants who take orders from junior officers, who 

 obey superior officers, who in turn obey orders 

 ultimately emanating from the council at the \\'ar 

 Office, indirecth". then, this council issues orders 

 to each indi\idual soldier in the army. Similarly 

 the brain is in touch with each muscle, which it also 

 drills and exercises and keeps in readiness for future 

 activity, a state we call "tone." The muscles, if 

 not in constant functional connection with the nerve 

 centres through the efferent nerves, woukl becotue 

 toneless, slack, unready to contract when a motor 

 impulse (command to action) arrived. Ikit the very 

 opposite is what we find : muscles duly inner\ated 

 have a certain degree of tension, are ready to shorten 

 after onl\- an exceedingly brief time from the instant 



of receiving the message. 



Muscles not thus 

 innervated, even though well suj^plied with blood 

 would not be in a perfect state of health, would 

 become "a law unto themselves," and therefore be 

 unrelated to their neighbours" needs. This unfailing 

 outflow of impulses from the cells of the central 

 nervous system to the periphery — to muscles, blood- 

 vessels, glands and possibly otfier tissues — is known 

 as innervation. Innervation really means being 

 attended to h\ the central nervous system : it is not 

 being given strength to do work, but it is being kept 

 in readiness to do work — a \cr\- different thing. It 

 is being neurallv supervised. Innervation is not the 

 commissariat : the blood supplies the food : the 

 blood is the canteen ; each muscle must absorb its 

 own nourishment, but b\- means of innervation it will 

 be constantl}- kept " up to the mark," drilled, made 

 tonic and read\- for action. Innervation is each 

 soldier"s knowing that those in authority over him 



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