368 ZOOLOGICAL PHILOSOPHY 



Since we cannot know what is actually the case on this subject, I 

 believe I have attained my purpose by showing what may be the case 

 or even probably is the case : for I can do no more. 



The wonderful composition of the hypocephalon, both in its main 

 features and in its individual regions, which are all duphcated, one 

 being in each hemisphere, is more than a mere hypothesis, in spite of 

 the fact that we lack the means for seeing it and assuring ourselves of 

 it. The organic phenomena constituting the intelhgence, and the fact 

 that each of these phenomena requires a special locahty in the organ 

 and indeed a special organ, so to speak, for its production, should give 

 us a moral conviction that the composition of the hypocephalon is as 

 I have represented it. 



Certainly, individuals are not born in possession of all their possible 

 intellectual faculties, for the organ of intelhgence, hke the rest, 

 develops according to its use. The same apphes with each special 

 kind of intellectual faculty : it is brought into existence in the 

 appropriate region of the hypocephalon by the needs that are felt ; 

 and in correspondence with the frequency of the repetition of these 

 acts, the special organ adapted to them develops and enlarges its 

 faculty. 



It is therefore not true that any of our intellectual faculties are 

 innate ; and this apphes also to those of our propensities which depend 

 on the faculty of thought. These faculties and propensities grow and 

 strengthen according to the exercise which we give to their underlying 

 organs. We may indeed derive certain tendencies from our inherited 

 organisation : but unless we exercise these faculties and inclinations 

 ourselves we gradually lose the aptitude for them. 



Dr. Gall having noticed that some individuals had particular 

 faculties, more developed and conspicuous than others, conceived the 

 idea of enquiring whether any part of their body might not present 

 some external signs by which this faculty could be recognised. 



He does not seem to have studied any faculties but those connected 

 with the intelligence ; for if he had he would have met with abundant 

 evidence that any part which is much exerted and has acquired a highly 

 developed faculty, always exhibits manifest signs of it in its size, shape, 

 and vigour. We cannot look at the posterior extremities and tail of a 

 kangaroo, without being convinced that these much used parts possess 

 great power of action, a fact which also apphes to the posterior legs 

 of grasshoppers, etc. In the same way, when we reflect upon the 

 immense growth of the elephant's nose, which has been transformed 

 into an enormous trunk, we cannot help recognising that the habitual 

 exercise of this organ, which is used by the animal as a hand, is account- 

 able for its size, strength, and wonderful suppleness, etc., etc. 



