It is usual with anatomists to join their observations and experiments on human bodies to those on beasts, and from the agreement of these experiments to derive an additional argument for any particular hypothesis.  It is indeed certain, that where the structure of parts in brutes is the same as in men, and the operation of these parts also the same, the causes of that operation cannot be different, and that whatever we discover to be true of the one species, may be concluded without hesitation to be certain of the other.  Thus though the mixture of humours and the composition of minute parts may justly be presumed so be somewhat different in men from what it is in mere animals; and therefore any experiment we make upon the one concerning the effects of medicines will not always apply to the other; yet as the structure of the veins and muscles, the fabric and situation of the heart, of the lungs, the stomach, the liver and other parts, are the same or nearly the same in all animals, the very same hypothesis, which in one species explains muscular motion, the progress of the chyle, the circulation of the blood, must be applicable to every one; and according as it agrees or disagrees with the experiments we may make in any species of creatures, we may draw a proof of its truth or falshood on the whole.  Let us, therefore, apply this method of enquiry, which is found so just and useful in reasonings concerning the body, to our present anatomy of the mind, and see what discoveries we can make by it.

In order to this we must first shew the correspondence of passions in men and animals, and afterwards compare the causes, which produce these passions.

It is plain, that almost in every species of creatures, but especially of the nobler kind, there are many evident marks of pride and humility.  The very port and gait of a swan, or turkey, or peacock show the high idea he has entertained of himself, and his contempt of all others.  This is the more remarkable, that in the two last species of animals, the pride always attends the beauty, and is discovered in the male only.  The vanity and emulation of nightingales in singing have been commonly remarked; as likewise that of horses in swiftness, of hounds in sagacity and smell, of the bull and cock in strength, and of every other animal in his particular excellency.  Add to this, that every species of creatures, which approach so often to man, as to familiarize themselves with him, show an evident pride in his approbation, and are pleased with his praises and caresses, independent of every other consideration.  Nor are they the caresses of every one without distinction, which give them this vanity, but those principally of the persons they know and love; in the same manner as that passion is excited in mankind.  All these are evident proofs, that pride and humility are not merely human passions, but extend themselves over the whole animal creation.