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From the unsuspecting credulity with which this textbook of the naturalists of the middle ages continued to be received, it is evident that the science remained stationary, if it did not actually retrograde, during the lapse of fourteen or fifteen centuries. The want of[xiii] opportunities of investigation may be regarded as the principal cause of this lamentable deficiency. Some of the rarer animals, it is true, were occasionally to be seen in Europe; but Menageries constructed upon a broad and comprehensive plan were as yet unknown. The first establishment of modern days, in which such a plan can fairly be said to have been realised, was the Menagerie founded at Versailles by Louis the Fourteenth. It is to this institution that we owe the Natural History of Buffon and his coadjutor Daubenton; the one as eloquent as Pliny, with little of his credulity, but with a greater share of imagination; and the other a worthy follower of Aristotle in his habits of minute research and patient investigation, but making no pretensions to the powerful and comprehensive mind and the admirable facility of generalising his ideas which so preeminently distinguished that great philosopher.

THE OCELOT.

But for these shades of colour, or for any other, we should look in vain in the animal of the Tower Menagerie, which, in consequence of a particular conformation, not unfrequent in some species of animals, and occasionally met with even in the human race, is perfectly and purely white. In order to explain this phenomenon, which is one of the most curious, but at the same time one of the most simple in physiology, it is necessary to observe that there exists beneath the epidermis, or outer covering of the skin, both in man and animals, a peculiar membrane of very fine and delicate texture, which is scarcely visible in the European but sufficiently obvious in the Negro, termed by anatomists the rete mucosum. In this net-work is secreted, from the extremities of the minute vessels which terminate upon its surface, a mucous substance which varies in colour according to the complexion of the individual, of the varieties in which it is the immediate cause; and from the substance thus secreted the colouring matter of the hairs and of the iris is derived. The pure whiteness then of the covering of the animal in question, and of all those which exhibit a similar variation from their natural tinge, is attributable solely to the absence of this secretion from whatever[195] cause. It is always accompanied, as in the present instance, by a redness of the eyes, arising from the blood-vessels of the iris being exposed to view in consequence of the want of the usual coating formed by this secretion, by which they are naturally protected from the too great influence of the light. In the human race the individuals who are thus afflicted, characterized by the dull whiteness of their skins, the deep redness of their eyes, and their colourless, or, as it is generally termed, flaxen, hair, are called Albinos. They are generally timid in disposition, languid in character, and weak both in mind and body. The same original conformation, for it is always born with the individual and never acquired in after life, although sometimes prolonged beyond its limits in the shape of an hereditary legacy, is common to many animals. Perhaps the most familiar instances among these are the white mice, the white rabbits, and the white pigeons, which are known to every one. But it has also been occasionally seen in many other species, as monkeys, squirrels, moles, pigs, and even cows and horses, and, to come a little closer to our present subject, in goats and deer. Not even that massive and stupendous beast the Elephant is exempted from its influence. It can hardly be necessary to recall to the reader the title on which the ruler of millions of not uncivilized Asiatics, the Burmese monarch, prides himself more than on any other, inasmuch as it is the emblem of power and prosperity, that of Lord of the White Elephant; a title, which, while it demonstrates the fact of the existence of this deviation in the Elephant as well as in other animals, proves also[196] the extreme rarity of its occurrence. It has moreover been noticed in many species of birds.