SCIENCE AND MAN. 



103 



the terms better, afferent and efferent nerves. 

 The former carry impressions from the external 

 world to the brain ; the latter convey the behests 

 of the brain to the muscles. Here, as elsewhere, 

 we find ourselves aided by the sagacity of Mayer, 

 who was the first clearly to formulate the part 

 played by the nerves in the organism. Mayer 

 saw that neither nerves nor brain, nor both to- 

 gether, possessed the energy necessary to animal 

 motion ; but he also saw that the nerve could lift 

 a latch and open a door by which floods of energy 

 are let loose. "As an engineer," he says with 

 admirable lucidity, " by the motion of his finger 

 in opening a valve or loosening a detent can lib- 

 erate an amount of mechanical energy almost in- 

 finite compared with its exciting cause, so the 

 nerves, acting on the muscles, can unlock an 

 amount of power out of all proportion to the work 

 done by the nerves themselves." The nerves, 

 according to Mayer, pull the trigger, but the gun- 

 powder which they ignite is stored in the muscles. 

 This is the view now universally entertained. 



The quickness of thought has passed into a 

 proverb, and the notion that any measurable time 

 elapsed between the infliction of a wound and the 

 feeling of the injury would have been rejected 

 as preposterous thirty years ago. Nervous im- 

 pressions, notwithstanding the results of Haller, 

 were thought to be transmitted, if not instan- 

 taneously, at all events with the rapidity of elec- 

 tricity. Hence, when Hclmholtz, in 1851, af- 

 firmed, as the result of experiment, nervous 

 transmission to be a comparatively sluggish pro- 

 cess, very few believed him. His experiments 

 may now be made in the lecture-room. Sound in 

 air moves at the rate of 1,100 feet a second ; 

 sound in water moves at the rate of 5,000 feet a 

 second; light in ether moves at the rate of 186,- 

 000 miles a second, and electricity in free wires 

 moves probably at the same rate. But the nerves 

 transmit their messages at the rate of only 70 

 feet a second, a progress which in these quick 

 times might well be regarded as intolerably 

 slow. 



Tour townsman, Mr. Gore, has produced by 

 electrolysis a kind of antimony which exhibits 

 an action strikingly analogous to that of nervous 

 propagation. A rod of this antimony is in such 

 a molecular condition that, when you scratch or 

 heat one end of the rod, the disturbance propa- 

 gates itself before your eyes to the other end, the 

 onward march of the disturbance being announced 

 by the development of heat and fumes along the 

 line of propagation. In some such way the mole- 

 cules of the nerves are successively overthrown ; 



and if Mr. Gore could only devise some means of 

 winding up his exhausted antimony, as the nu- 

 tritive blood winds up exhausted nerves, the com- 

 parison would be complete. The subject may be 

 summed up, as Du Bois-Reymond has summed it 

 up, by reference to the case of a whale struck by 

 a harpoon in the tail. If the animal were seventy 

 feet long, a second would elapse before the dis- 

 turbance could reach the brain. But the im- 

 pression after its arrival has to diffuse itself and 

 throw the brain into the molecular condition 

 necessary to consciousness. Then, and not till 

 then, the command to the tail to defend itself is 

 shot through the motor nerves. Another second 

 must elapse before the command can reach the tail, 

 so that more than two seconds transpire between 

 the infliction of the wound and the muscular re- 

 sponse of the part wounded. The interval required 

 for the kindling of consciousness would probably 

 more than suffice for the destruction of the brain 

 by lightning or even by a rifle-bullet. Before 

 the organ can arrange itself, it may, therefore, be 

 destroyed, and in such a case we may safely con- 

 clude that death is painless. 



The experiences of common life supply us 

 with copious instances of the liberation of vast 

 stores of muscular power by an infinitesimal 

 "priming" of the muscles by the nerves. We 

 all know the effect produced on a "nervous" 

 organization by a slight sound which causes 

 affright. An aerial wave the energy of which 

 would not reach a minute fraction of that 

 necessary to raise the thousandth of a grain 

 through the thousandth of an inch, can throw the 

 whole human frame into a powerful mechanical 

 spasm, followed by violent respiration and palpi- 

 tation. The eye, of course, may be appealed to 

 as well as the ear. Of this the lamented Lange 

 gives the following vivid illustration : 



A merchant sits complacently in his easy-chair, 

 not knowing whether smokmg, sleeping, news- 

 paper-reading, or the digestion of food, occupies 

 the largest portion of his personality. A servant 

 enters the room with a telegram bearing the words, 

 " Antwerp, etc. . . . Jonas & Co. have failed." 

 " Tell James to harness the horses ! " The ser- 

 vant flies. Up starts the merchant wide awake, 

 makes a dozen paces through the room, descends 

 to the counting-house, dictates letters and for- 

 wards dispatches. He jumps into his carriage, 

 the horses snort, and their driver is immediately 

 at the bank, on the Bourse, and among his com- 

 mercial friends. Before an hour has elapsed he 

 is again at home, where he throws himself once 

 more into his easy-chair with a deep-drawn sigh, 



