THE NERVOUS SYSTEM AND THE INTELLECT. 



275 



mechanical cause. The case of the skull, in which 

 the brain is inclosed, is framed out of a certain 

 Dumber of bones that remain disconnected with 

 each other till the age when the brain itself ceases 

 growth ; but it sometimes happens that these 

 bones unite too early, and so prevent all develop- 

 ment of the brain, thus shut up in a space too 

 confined for the size it should gain. Then the 

 instrument is spoiled, philosophers say, and can 

 do no more service ; then, say the biologists, the 

 relations no longer exist in the inner structure of 

 the organ that are necessary for the play of the 

 functions it was designed for. It is strange that 

 physiology has not yet bethought itself of pro- 

 ducing artificial idiocy in animals. No one nowa- 

 days doubts that animals have a mind, less perfect 

 certainly than ours, but still with a possibility of 

 comparison with our own. They have our pas- 

 sions : they love, hate, remember, sometimes 

 show sense even, without borrowing from fable- 

 writers ; they dream, beyond any question ; there 

 are some that may be certainly considered as 

 going mad, some willingly get intoxicated. Prob- 

 ably it would be easy to make animals idiotic at 

 will by checking the development of their heads, 

 as the Chinese make distorted feet by using lead- 

 en shoes that compress their growth. 



It is known that the number of nerve-cells, of 

 white tubes, and all the microscopic elements 

 from which the brain is built up, increases up 

 to a certain age. As we advance in life, then, 

 new connections are established between the dif- 

 ferent parts of the brain ; it is a natural conclu- 

 sion that this improvement of the organ is linked 

 with the development of our faculties. It is no 

 more unreasonable to admit that connections of 

 the same kind continue to be set up in one di- 

 rection rather than in another, in the degree that 

 we exercise a given faculty, as the muscles of an 

 artisan become with time better disposed for the 

 daily work they have to do. We have not, in- 

 deed, and shall not have for a long time, the di- 

 rect proof that such is the case — that, little by 

 little, our intellectual labors, the aptitudes that 

 we strive to develop in ourselves, induce more or 

 less deep modifications in the inner structure of 

 the gray or white matter of our brain. This sup- 

 position might even seen entirely gratuitous, did 

 not a well-known fact come up in proof that it is 

 well founded. Inheritance, the reappearance in 

 the descendant of the features or any other phys- 

 ical mark of the ancestor, is not accounted for. 

 This, again, is one of those peculiarities of living 

 bodies that we must be content to note ; but de- 

 scent transmits, also, as numberless instances 



prove, the mental aptitudes as well as the bodily 

 marks. Now, it is very hard, strive as we may, 

 to explain in any other way than by the inheri- 

 tance of a material structure, the reproduction 

 in the descendant of the moral or intellectual 

 qualities acquired by the ancestor. Descent, 

 creating a bond by means of generation between 

 two " souls," two purely spiritual essences, is a 

 sort of metaphysical nonsense, while it is an 

 entirely natural statement, as applied to the 

 deeper formations of the brain, as well as to the 

 features of the face. If biologists profess to see 

 in that transmitted modification the very source 

 of the resemblance between two generations in 

 their aptitudes and powers, the partisans of the 

 contrary opinion will find no lack of explana- 

 tions. Like an instrument under a master's bow, 

 the brain, practised by degrees, yields more, be- 

 comes more flexible, more vibrating under cer- 

 tain notes. These qualities, all of them material, 

 are the ones that are transmitted, and the instru- 

 ment appears again in the next generation, bet- 

 ter fiited to give the same tone, when played 

 upon by an intelligence which is constantly equal 

 and the same in all men. If it is true that the 

 brain, like the other organs, may be modified in 

 this manner by the habitual exercise of a faculty 

 or an aptitude, and that its modifications may be 

 hereditary, these two facts of themselves are suf- 

 ficient to explain instinct. 



v. 



It has already been remarked, as to the theo- 

 ry of these successive transformations of exter- 

 nal contacts into unconscious sensations, of the 

 latter into perceptions, and thus successively into 

 idea and volition, down to the setting at work of 

 the muscles, how nearly that theory harmonizes 

 with late physical discoveries in the transforma- 

 tion of forces. If a very little attention is given 

 to this physiological chain of sequence, more 

 than a mere analogy will be perceived in it. At 

 both extremes of the circuit traveled by the ner- 

 vous influx we find the outer world. Let us go 

 back to the instance of the beheaded subject, 

 which is always instructive, because the condi- 

 tions of the case presented are relatively very 

 simple. His hand is stretched motionless on the 

 table ; when quickly touched with a hot iron, it 

 draws back, making a movement in which we 

 may see the mechanical equivalent of the caloric 

 thrown off by the metal. Yet the transformation 

 is not direct ; it has gone through at least two 

 nervous acts in the spinal cord. The disengaged 

 caloric became at first an unconscious sensation, 



