The wool fibre is curly, and to a certain extent elastic. Its aurface is covered with scales or imbrioations, differing in number and shape according to the apecies and even variety of the animal from which the fibre has been obtained. The most important differences also exist in the fleece of the same animal, which fact renders necessary the process of aorting. Between wool snd hair, the differences are even greater still. In the latter, the acsles or imbricationa are so imperfectly developed, even if in some sorts they exist at sll, that the article until quite recently haa been incapable of use in the same way as wool. Recent improvements in the manipulation have, however, led to the successful introduction of hair for purposes of admixture wool, and its use is now rapidly growing. Those which have been received with most favour, and have, either alone or mixed, beeu most successfully used, are the hairs of the alpaca, the llama. the vicuna, the Angora goat, and the camel, which are all more nearly allied to wool in structure than uther animal hairs. Fig. 1437 sufficiently illustratea the mechanical structure of the wool fibre, and its variations in the different varieties of sheep.
The figures are to some extent typical: A is from a fleece of the celebrated merino variety of sheep, for which the modern world is so deeply indebted to Spain; the characteristics of this wool may be summed up briefly as follows : staple, short; quality, very fine ; colour, generally white; most suitable for carding purposes. E is a fibre of Saxony wool, the animal yielding it being a sub-variety of the preceding, a cross between the merino and the best native sheep of Saxony. The wool produced by these animals demonstrates the advantage of high and careful culture, being classed along with Silesian, a similar sub-variety of the merino, the finest wool in the world. Its characteristics resemble those of A. It is sometimes used for combing purposes. The Southdown (B), and those breeds of which it forms the basis, constitute a variety of the common sheep. Its wool is in all cases short and fine, except where it has been purposely crossed with long-woolled varieties in order to procure a medium wool. The product is used for both combing and carding. The Leicester (C) and Lincoln (D) represent our long-woolled varieties of sheep. The staple is long, and the quality ranges from coarse to very fine. In Yorkshire, Nottingham, Lincoln, and Leicester, these two varieties yield a highly lustrous wool, approaching mohair (H) and alpaca in brilliancy. These are technically known as " lustre" wools. So far aa ia known, this wool can only be grown in the four counties above named. When the pure Lincoln or Leicester sheep are transferred to other countries, or even other parts of England, the fleece rapidly loses its brilliancy. Common wool (F), goat-hair (G), cow-hair (I), and human hair (J), are also shown.
The carding or short wools are distinguished by a finer fibre and a greater number of imbrications per lineal inch, Saxony and Silesian wools being only v-ST, -Irk, in. diam., 3-3i in. in length of flbre, and having 2700-2800 imbrications an inch. Merino falls a little below these, and Southdown as much further, the last-named being rii; in. diam., and. having only about 2000-2100 serrations in an inch. When a wool flbre has a less diameter than 3-1--,„ in., it is denominated a coarse wool, and so regarded in the trade ; as the length of staple increasea, the number of imbrications These ohanges render it unfit for clothing purposes, as its felting property is thereby reduced.
It is believed that the method of growth of the wool fibre is somewhat as follows. The skin of most auirnals is organically formed for the production of hair, in this term including wool. The length and thickness of the hair is regulated by a law of nature, and is perfectly adapted for its purpose, changing in several respects in the different parts of the body. The shape varies in different animals, but is genemlly cylindrical or oval. The tip of the hair at Brat ie conical and pointed, this being, as is well known, the distinguishing characteristic of the first or " hogget " fleece of sheep. When left to nature, wool- and hair-bearing animals cast their coat at appropriate seasons, and soon assume a new one. This seems to be caused by a cessation of activity in the secreting glands at their base or root, whereby the hair becomes detached, and is cast off. After a period of rest, the aecreting and excreting functions of the glands are resumed, and the new covering soon beoomes visible. Domestication of animals, especially when shearing the fleece or clipping the hair becomes habitual, interferes with the natural intermittent activity of the hair glauda, which instead become persistent, and the growth continuous. In the human subject, to whioh moro attention has been given than to animals, and in whioh the growth of hair is closely analogous, it has boon found that at the bottom of each hair-tube is a small conical prominence, like a papilla of the sensitive layer of the derruis, with which latter it is conneoted by nicans of the walls of the sheath or bair-tube. This cone is the producing organ of the hair, and posaessea a large number of oapillary vessels and nerves. The hair-pulp is seoreted in this cone, and, being poured out, is first oonverted into granules, and next into cells, which are subsequently modified to constitute the texture of the hair. The cells contain the pigment upon which the colour. depends. In the structure of the hair, a threefold modification of the cells taken place.