wool-bearing creature, it would appear as liable to be entirely destitute of it as some other animals; for in Tartary, the eastern parts of India, China, and some parts of Africa, a hair of varying quality forms their sole covering; and Sir Joseph Banks imported three from Spain, which were smooth, sleek, and as short-haired as a horse.

(25.) Structure of the Skin.—The skin is composed of three coats, or layers; the outermost, the cuticle or scarf-skin, is a thin delicate membrane, devoid of feeling, and of a scaly texture, pierced by innumerable small holes, for the passage of the hairs, and perspiration, and covering the next, or mucous coat, so named from its pulpy appearance. In this resides the colouring matter, which imparts its peculiar tints to the hair, and which can only be satisfactorily demonstrated in the dark races. The existence of this coat has been by some denied; but it is probable that, though present in all, it can only be exhibited in such as have depth of tint, to admit of the display. It is here that sensation principally resides; the nerves, or rather their terminations, ramifying minutely in its substance, at which they have arrived by piercing the third tunic, or true skin, a dense firm elastic membrane, in which the roots of the hairs are imbedded, and from which, in fact, they take their origin.

(26.) Sebaceous Follicles.—The skin is studded over by small glands, or what, in anatomical language, would be called sebaceous follicles, which vary in number in different breeds, and different parts of the body, being most numerous on the breast and shoulders, and secreting a peculiar unctuous semi-solid matter, which, as we shall immediately see, possesses alkaline properties.

(27.) Connection of the hair with the skin—Yolk.—A hair implanted in the skin may be compared to a plant growing in a flower-pot which has been sunk in the earth, as the root of the hair does not rise directly from the true skin, but from a little cup extending from it to the cuticle, and receiving nourishment from surrounding vessels. After coming to the surface of these tunics it has, in the sheep, yet another, and, in some respects, remarkable covering to pierce, one which has occupied the attention of the most distinguished chemists, and given rise to a good deal of disputation on the subject of salving—we allude to the Yolk. It is supposed by many to be the inspissated secretion of the sebaceous follicles, and receives its name from its adhesiveness and colour. It is most plentiful on fine-woolled sheep, those of the south possessing more than those of the north of our island, while merinos possess most of all; so that there is apparently some connection between a fine fleece, and a good supply of this matter. According to the analysis of M. Vauquelin, it consists principally of a soapy matter, with a basis of potash; a small quantity of carbonate of potash; a minute quantity of acetate of potash; lime in an unknown state of combination; and an atom of muriate of potash. It owes its odour to a small quantity of animal oil, and is in every respect a true soap, which would permit the sheep to be completely washed in a stream, but for the existence in the fleece of an uncombined fatty matter, which remains attached to the wool, and renders it rather glutinous.

Many have tried to account for the uses of the Yolk, but nothing like satisfactory conclusions have been come to: some considering it goes to form the filament, and is consolidated into a transparent mass while the pile is growing; while others argue, that it is a peculiar secretion which exudes through the skin, and by mixing with the pile renders it soft and pliable, affecting it in the way that oil does a piece of leather. In the latter opinion I coincide. For my part, I view it as a secretion, depending very much on good food and steadiness of temperature, and, therefore, indicative of a fine fleece only so far as the health of the animal is concerned. In the human being the state of the skin may often guide us, though blind-fold, to the quality of the hair, so that the latter may be pronounced either dry and coarse, or glossy, soft, and silky, as the skin may prove either harsh and ungrateful, or pleasant, and, if I may be allowed the expression, alkaline to the touch. Every thing having a tendency to affect the health may always be considered as calculated to diminish this secretion, and, consequently, to deteriorate the quality of the wool.

The relative positions of the layers of the skin, the mode in which the hairs rise from them, and the form and situation of the sebaceous follicles, will be better understood by referring to the following cross section Fig 5. Pl. V., in which the line marked

• a Represents the cuticle,
• b The mucous layer,
• c The true skin,
• d Sebaceous follicles,
• e Hairs rising from the true skin and inflections of the upper layers and piercing,
• f The thin film of the yolk.

(28.) Periodical decidence of Wool.—It is affirmed that the only real difference between hair and wool is in the latter falling off periodically; but the same change takes place in animals totally covered with hair; in fact, almost every animal is subject to moulting, or a periodical decidence of its protecting covering. The fleece of the sheep has been proved in many instances not to be liable to annual changes of this description;—Lord Western having, among others, shown that the wool of the merino may be retained at least three years without the slightest disposition to separate.

The annual employment of shearing, to anticipate this falling off of the wool, is now common in most parts of the world; yet some, as the Icelanders and Kamtschadales, still retain the primeval custom of rowing, or pulling off the fleece in a mass, about the end of May, at which time it is nearly loosened. This loosening of the attachments of the fibre is supposed to be owing to a diminution, during winter, of the nutritive process at the root of the hair, so that the fibre is liable to give way at the tender part when the fleece becomes heavy during Spring. This attempt at an explanation meets, however, with the insurmountable objection, that long-woolled are less liable than short-woolled sheep to this occurrence, a circumstance which ought to be the reverse, if weight had any thing to do in the case.

(29.) Falling off of Wool prevented by Clipping.—Clipping has a curious influence over the duration of the covering of animals, as is well exemplified by the correct popular idea, that the only way to prevent the hair of children dropping off (as it sometimes has a tendency to do) is to cut it short: we may suppose the benefit in this case to result from the removal of a portion of each hair, which, if allowed to remain, would lead to a sacrifice of the whole, by robbing the root of a quantity of nutritious matter, which, owing to a diminution of reproductive power, it could ill afford. In this way only can we account for the power which shearing evinces, in putting a stop to the attempt sometimes made by nature to change the coverings of some sheep. In the valley which separates the most eastern chain of the Cordilleras from the central, the wool grows upon the lambs in the same manner as in temperate climates, provided they are sheared so soon as it has arrived at a certain thickness; in which case the wool grows again, preserving the same order. But, if the period for denuding the animal be allowed to pass, the wool detaches itself in flakes, leaving behind a short, glossy, and compact hair, exactly resembling that of the common goat in the same climate.

(30.) Form of woolly fibre.—The fibre of wool is circular, differing in diameter in the various breeds, and different parts of the same fleece. The following à propos observations are from the article on the Sheep, in the Library of Useful Knowledge: "The filaments of white wool, when cleansed