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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



secret nerve-actions, will at some future day give 

 us an explanation of cerebral functions by the 

 simple physical or chemical laws that govern un- 

 organized bodies ? By no means, and we desire 

 to give this negation all the emphasis possible, 

 that it may be thoroughly understood, and strong- 

 ly impressed upon the reader. Physiology will 

 be able to make all imaginable discoveries as to 

 the relations, the succession, the duration, of men- 

 tal acts ; it will not be able to form even an opin- 

 ion as to the essential nature of those acts. It 

 connects them with a special peculiarity of the 

 living nerve-matter. ' It proves the existence of 

 that peculiarity, and studies its effects in the 

 measure in which they manifest themselves to us, 

 and that is all. Every tissue that helps to make 

 up our body thus, has properties which are pe- 

 culiar to itself, and are equally inexplicable. A 

 living muscle contracts when it is influenced by a 

 nerve or an electric spark. We call this proper- 

 ty it possesses, contractility, but we know noth- 

 ing of it but its effects, and we examine nothing 

 else. We call elasticity that property through 

 which an ivory ball, pressed out of shape by fall- 

 ing on marble forcibly, resumes a spheroid form ; 

 but in neither case do the names we give to the 

 properties of the bodies define their nature ; and, 

 if there could be degrees in our ignorance in these 

 respects, the properties we recognize as peculiar 

 to living bodies would be less plain than those 

 they share with inanimate bodies. 



It is from neglect to make this clear distinc- 

 tion between properties common to all bodies 

 without exception, such as extension, color, elec- 

 tricity, and properties special to living substances, 

 such as contractility, nutrition, power of growth, 

 and reproduction, that biologists have suffered 

 the undeserved reproach of seeking the explana- 

 tion of life in the laws of brute matter, in spite of 

 the truth that their efforts, on the contrary, tend 

 to draw a plain broad line betwen these two or- 

 ders of facts. 



Before closing, should we speak of that com- 

 parison, attributed to a great author by writers 

 who never read him, between the brain and a 

 gland-secreting thought ? Cabanis never said 



anything like that, as any one may satisfy him- 

 self from his memoir presented to the Academy 

 in the year 5. The passage so unfairly quoted, 

 on the contrary, is most significant. Cabanis an- 

 swers those who maintain that our inability to 

 understand how the mind acts compels us to be- 

 lieve with Plato that it is of divine origin, that on 

 that ground we are by no means at the end of our 

 no-knowledge, and that the movements of the 

 stomach, the digestion of food are also of divine 

 essence, because they are quite as incomprehen- 

 sible ; he simply compares external impressions 

 to food conveyed to the brain ; worked over and 

 digested by it, and returned by it " metamorphosed 

 into ideas which the language of the features and 

 gestures, the signs of words and writing, manifest 

 outwardly." In truth, in Cabanis's time nothing 

 could be better said ; and modern Science, as we 

 have seen, has by no means rejected that notion 

 of an elaboration by the brain of external im- 

 pressions which are then sent back to the outer 

 world under a new form. A doctrine has been 

 constructed, almost, out of a comparison used by 

 Cabanis to make his thought plainer. He knew 

 better than those who attack him what a gland 

 is, and that a secretion is always a ponderable 

 body, as bile, for instance. To charge him with 

 the opinion that he took thought to be such a se- 

 cretion, is as if he were made to say, for instance, 

 that muscles secrete contractions, and bones re- 

 sistance. Thought, imagination, memory, dreams, 

 the will, all result from a peculiar property, un- 

 known in its essence, as all others are, and with 

 which the nerve-substance is endowed. An Eng- 

 lishman, Lewes, some time ago proposed for it 

 the name of neurali/i/, to class with the words 

 contractility, elasticity, etc. As to the essence 

 of this property, and of all the others, biology 

 leaves to metaphysicians that convenient theme on 

 which, from Plato's time to Descartes's, they have 

 written variations that have persuaded the world. 

 For itself, it does not study first causes, forever 

 hidden from our research, but effects, and at this 

 day it can discern in its first conquests in this 

 wholly new region the foundation of a new science 

 which the future will call scientific psychology. 



