The ganglions differ essentially from the brain in the early periods in their development, which is proportionably much less advanced than that of the brain. They are only on a level with all the other organs, whilst this is infinitely superior to them in this respect, as we have seen. By comparing the superior cervical, semilunar ganglions, &c. in the fœtus, and in the adult, it is easy to make this remark. The ganglions receive also less vessels in proportion than the brain. They do not follow the proportion of increase of the organs to which they send nerves. Thus those that furnish the genital organs, which are nearly nothing during the first years of general nutrition, are as large in proportion as those which go to the liver, the stomach, the intestines, which are characterized by an early increase. These nerves follow in this respect the same law as the ganglions, though the most are found upon the arteries, which are more or less developed according to the organs they penetrate. The nervous system of organic life being less early in its development than that of animal life, should be subject in infancy to fewer affections; and this is what is observed. Convulsions, and most of the neuroses of the second, are, as we have seen, a peculiar appendage upon infancy. On the other hand, the particular order of nervous affections of which we have spoken, and in which it appears that the first takes the principal part, is generally less frequent at this period. All nervous diseases, whose peculiar seat seems to be at the epigastric region, in which there is so great an abundance of nerves coming from the ganglions, appear to be foreign to this age. Another difference that distinguishes the ganglions from the brain as it respects development, is this, that in the fœtus, they are not, like it, of extreme softness. Their hardness is little inferior to what they afterwards possess in adult age. In proportion as we advance from infancy, the organic nervous system begins to become predominant. It is towards the thirtieth or fortieth year that it appears at its maximum of action; it diminishes as we approach old age; it decays in part at this epoch. The nerves become greyish; the ganglions are hard, resisting and smaller. The neuroses that appear to belong to them are infinitely more rare. Moreover, the obscurity that rests upon the functions of this system, does not allow me to point out definitely the alterations they experience in the different ages. V. _Remarks upon the vertebral ganglions._