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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



then a motive stimulus, then a movement. The 

 transformation, immediate in the material world, 

 is mediate, therefore, through the organism ; but 

 it is not the less real. Nervous acts, in the last 

 statement, then, would be only transformations, 

 peculiar in kind, of the forces of the physical 

 world. The problem is far from being set before 

 us as simply as we here state it, yet it seems that 

 the solution can inspire no doubts. Whether the 

 external impression — that of caloric or any other, 

 it makes no difference — results in an involuntary 

 motion of the beheaded subject, or in a conscious 

 perception of the man with his head on his shoul- 

 ders, the nervous act in either case represents an 

 equivalent of the forces that govern the physical 

 world. Any muscular movement (we take here 

 the simple fact, but the same can be said of the 

 secretions, of transpiration, etc.) may be regarded 

 as a restoration to the exterior, in the form of 

 mechanical equivalents, of all the influences re- 

 ceived from the exterior in the form of impres- 

 sions ; but, once set out in that path, physiolo- 

 gists had no reason to stop. Pushing their de- 

 ductions to the end, they asked whether all these 

 intermediate nervous acts, thought, imagination, 

 must not be regarded as making part of continu- 

 ous series whose starting-point would always be 

 connected with an external impression, and whose 

 closing-point must inevitably be an action upon 

 the external. In reality we do not maintain that 

 there is always, from one extremity to the other 

 of the circuit, a regular chain of effects. The 

 amount of impressions accounted for is some- 

 times considerable, as in reading, in hearing a 

 piece of music, and the nervous expenditure is 

 also sometimes considerable in acts in which we 

 do not suspect it, as in walking. The foot can- 

 not be lifted without the passage of thousands 

 of excitements issuing from the nervous centres 

 to produce contraction of the muscles ; we can- 

 not hold ourselves upright and erect without a 

 labor of the brain. This cerebral activity, of 

 course, is unconscious in bodily exercises, yet it 

 is very real, and it explains how the brain needs 

 the restoration of sleep after muscular fatigue, 

 as well as after great mental labor. 



But the important question is not even to 

 learn whether all nervous impressions result more 

 or less rapidly, more or less slowly, in voluntary 

 acts, whether they are all returned to the exte- 

 rior ; it is certain that they are so, at least partly. 

 The other side of the problem is the interesting 

 one, Do all our thoughts necessarily make a part 

 of these continuous series ? Are our imagina- 

 tion, our most abstract ideas, all merely more or 



less direct results of external impressions? — in a 

 word, is the ancient axiom, " There is nothing in 

 the mind but what has been in the senses," the 

 expression of a physiological truth ? Or is just 

 the reverse true, and may these inmost cerebral 

 acts originate spontaneously at some point of the 

 circuit, the gray matter drawing from the supplies 

 of blood nutritive principles that suffice for its 

 special activity, apart from all stimulus ? On 

 this capital point physiologists disagree. 



Those who maintain that the origin of our 

 ideas is to be traced to external impressions in- 

 sist on the infinite number of these which we are 

 not conscious of. While I am writing, the street- 

 noises reach my ear, and affect it ; I receive them, 

 then, yet I do not hear them. Two friends in 

 conversation during a walk in the country are 

 discussing some serious problem of linguistics in 

 sight of a brilliant sunset, which they do not re- 

 mark, and yet the whole panorama of splendors 

 unfolded before them is exactly painted on their 

 retina. Who knows whether one of these talk- 

 ers, a charming historian, will not, some later 

 day, discover in his imagination the glorious pict- 

 ure received that evening by his eyes alone ? All 

 our senses are every moment attacked by a 

 throng of impressions, the great majority of 

 which pass unperceived. What becomes of 

 them ? For the retina, the ear, once impressed, 

 must have reacted within us, in one way or an- 

 other ; to admit the contrary, would be to deny 

 that law of permanence of forces to which, as we 

 learn more clearly every day, life as well as the 

 physical world is subject. We may conjecture, 

 then, that in the nervous system they follow a 

 different circuit from that which would have 

 made perceptions of them, and remain somewhere 

 stored away, like facts kept by the memory, with 

 this difference, that we possess neither the con- 

 sciousness nor the free disposal of this wealth. 

 Then, at a given moment, under unknown influ- 

 ences, they reenter, like a stray telegram, into 

 the current of conscious nervous acts, whether 

 returning grouped in the natural order in which 

 they were received — being in this case reminis- 

 cences — or, coming back irregularly and in lawless 

 confusion, and then being delirium, or dreams. 



Those who maintain the contrary opinion, hold- 

 ing that such or such a part of the gray matter 

 may set to work of itself, by a kind of automatic 

 function, do not need thus to take notice of those 

 unconscious impressions on which the system of 

 their opponents rests. Any particular part of 

 the brain, instead of fulfilling the simple duty of 

 transforming a received impression, may by its 



