(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.