A Discourse on the Soul and Instinct

TO THE AUTHOR'S COURSE OF LECTURES ON THE INSTITUTES OF MEDICINE AND MATERIA MEDICA, IN THE UNIVERSITY OF

THE CITY OF NEW YORK,

FOR THE SESSION OF MDCCCXLVII-VIII.

DELIVERED ON THE EVENING OF OCTOBER 28, 1847.

PUBLISHED ORIGINALLY BY THE MEDICAL CLASS.

"The Science of Nature, rightly interpreted, is the knowledge of things through their causes." "Effects are frustrated by an ignorance of their cause; but a knowledge of the cause becomes a rule in practice."-LORD BACON.

DISCOURSE, &c.

IN looking abroad upon organic nature, its most remarkable feature is the variety by which it is distinguished. So great, indeed, is the diversity of form, of organization, and of vital characteristics, the careless observer regards the assemblage as a mass of heterogeneous objects which have few affinities, and often without a remote relationship. He looks upon man as fundamentally distinct from the brute; and whenever specific differences are strongly marked, the same isolation obtains as we descend in the scale of existences. Coming, at last, to the vegetable kingdom, there is so little apparent analogy with the prominent features of the animal race, that none but the physiologist can detect a shadow of resemblance between the two departments of the organic kingdom. How different, however, with him who has explored the whole by the light of science. Whatever the color or the conformation of man, he is always endowed with certain attri

butes which give to the critical inquirer as perfect an assurance of identity of species as the clearest demonstration enables the ignorant to decide that there is no other difference than color in a brood of chickens.* By the same course of observation the philosopher, after descending along the thousands of species which make up the tribes of animals, finds himself wonderfully imitated in form, structure, and functions, by apes and baboons, and taking in his way other species which are as nearly allied to the ape as the ape is to

same.

* I need scarcely say that all the essential attributes of species are common to the whole human family, and that this rule of identity must obtain with man as with the different species of animals and plants. In organization, the nature of food, the relative proportions of atmospheric air concerned in respiration, the character of the secreted and excreted products, and in every fundamental point, the several races of mankind are exactly the We know, also, that no varieties of species, either of animals or plants, have been created, but that all the varieties, so far as known, have been the result of the gradual operation of physical causes. These may not have given rise to the color of the Negro, nor is it probably owing, as supposed by many, to the mark set upon Cain. (See Medical and Physiolog. Comm., Vol. 2, p. 640.) But the fact in relation to Cain allows a consistent supposition that the color of the Negro may be of the same miraculous nature; while the facts which identify the human race as one species are incontrovertible. Besides those which are relative to organic nature, I have set forth another, in the Institutes of Medicine, which, in itself, seems to be conclusive of the common descent of mankind. That fact consists in the coincidence