In the second place, whenever a nerve traverses a mass of gray matter, it receives from it, according to Gall, certain new nervous filaments; and in this way it grows and developes itself. The cerebrum and cerebellum will not fail therefore to grow and be developed likewise. The primitive bundles of the cerebellum, (the restiform bodies,) will grow by means of the filaments which will be imparted to them by the gray matter of the ciliary body: the primitive bundles of the cerebrum, (the pyramidal eminences,) by the filaments imparted to them by, first, the gray matter of the pons varolii; secondly, by that of the optic strata; and then by that of the olivary bodies, corpora striata, &c. &c.
Finally, in the same manner as a nerve of sense expands at its termination, and by means of such expansion forms the organ of the sense, so the primitive bundles of fibres of the brain and of the cerebellum terminate in expansions, and constitute the organs of the internal senses; that is to say, the lobes of the cerebellum and the hemispheres of the brain.[186]
NOTE II.
Difference between Instinct and Understanding.
[Page 64 (Note).] And he does not see that as to the instincts and the understanding all is contrast.
Here is what I have elsewhere said upon this question, so long debated, of the instinct and understanding of animals.
“There is a most complete difference between instinct and understanding.
“In instinct all is blind, necessary, and invariable. In understanding every thing is elective, conditional, and modifiable.
“The beaver which builds its house, and the bird that constructs its nest, act only by instinct.
“The dog and the horse, that learn even the meaning of several of our words, and who pay obedience to us, do so by understanding.