Page:Popular Science Monthly Volume 7.djvu/63

Rh other portions of the system, shows such marked relations to the complexity and perfection of the movements of which any animal is capable, as to render it nearly certain that its use is to regulate and coordinate muscular action; while the former, as marking a grand advance in the psychic endowments of living creatures, constitutes the most important addition to the nervous system hitherto found.



Here, for the first time, inclosed in its bony covering, we have an <organ possessing, even in a rudimentary form, the principal parts of a complete brain. Of these parts the cerebrum, which is found as merely rudimentary in the fish, now takes the precedence in interest and importance—from fishes to reptiles, from reptiles to birds, from birds to mammalians, and all through the mammalian tribes, from the imperfect marsupial upward to the anthropoid apes and man, we find in the main, an unbroken line of increase in cerebral development, and corresponding increase in intelligence.

Then, again, it is of interest to inquire the manner in which this new faculty, intelligence, makes its appearance along with the improved nervous organization, and how it differs from the instinct of the classes below.

According to the eminent authority before referred to, as instinct is the aggregate experience of the race, accumulated and impressed upon the nervous system by innumerable repetitions, inherited by each individual of the race and available all at once, so intelligence is the aggregate individual experience and is available only as acquired, though the facility for acquiring it varies according to the nervous organization. Both instinct and intelligence may exist in the same individual, but generally, in proportion as actions governed by intelligence become numerous, those governed by instinct decrease in number and importance. In observing the nervous organization of the