Those animals which conceal themselves[316] at certain periods of the year, as already mentioned, have no blood at those times, with the exception, indeed, of some very small drops about the heart. A marvellous dispensation of Nature! and very similar to that witnessed in man, where the blood is sensible of various modifications from the slightest causes; for not only, similarly to the bile, does it rush upwards to the face, but it serves also to indicate the various tendencies of the mind, by depicting shame, anger, and fear, in many ways, either by the paleness of the features or their unusual redness; as, in fact, the redness of anger and the blush of modesty are quite different things. It is a well-known fact, that when a man is in fear, the blood takes to flight and disappears, and that many persons have been pierced through the body without losing one drop of blood; a thing, however, which is only the case with man. But as to those animals which we have already mentioned as changing[317] colour, they derive that colour from the reflection[318] of other objects; while, on the other hand, man is the only one that has the elements which cause these changes centred in himself. All diseases, as well as death, tend to absorb the blood. CHAP. 92. (39.)—WHETHER THE BLOOD IS THE PRINCIPLE OF LIFE. There are some persons who are of opinion that the fineness of the wit does not depend upon the thinness of the blood, but that animals are more or less stupid in proportion to the skin or other coverings of the body, as the oyster and the tortoise, for instance: that the hide of the ox and the bristles of the hog, in fact, offer a resistance to the fine and penetrating powers of the air, and leave no passage for its transmission in a pure and liquid state. The same, they say, is the case, too, with men, when the skin is very thick or callous, and so excludes the air. Just as if, indeed, the crocodile was not equally remarkable for the hardness of its skin and its extreme cunning. CHAP. 93.—THE HIDE OF ANIMALS. The hide, too, of the hippopotamus is so thick, that lances,[319] even, are turned from it, and yet this animal has the intelligence to administer certain medicaments to itself. The hide, too, of the elephant makes bucklers that are quite impenetrable, and yet to it is ascribed a degree of intelligence superior to that of any quadruped. The skin itself is entirely devoid of sensation, and more particularly that of the head; wherever it is found alone, and unaccompanied with flesh, if wounded, it will not unite, as in the cheek and on the eyelid,[320] for instance. CHAP. 94.—THE HAIR AND THE COVERING OF THE SKIN.