Seal the fur' gets scanty in the adult (Otaria lobata, e.g.); in others it continues abundant in quantity, and of fine quality (Otaria ursina, e. g.); hence a difference in the commercial value of the skins, whereby sealers' distinguish between the hairseals' and the fur-seals.'

The term 'wool' is commonly understood to mean the modified hairs of domesticated breeds of sheep, which, through a finely imbricate arrangement of superficial serrated scales, and a curly disposition, have the property of mutual cohesion, called 'felting,' on which depends the value of wool in manufactures. The property is present in a minor degree in the longer, straighter, scantier fleece of such wild sheep as the Himalayan Oris Vignei, the Ovis Ammon of Central Asia, and the Oris Musimon of Sardinia. In the domesticated races the fleece has been modified and improved, in various degrees, by crossing the breeds, by choice of climate and pasture, and by careful attention and defence during its growth, until not only has the original coarse character of the product disappeared, but qualities of wool of different kinds and of different degrees of superiority have been obtained, generally divisible into two classes, one better adapted for carding,' the other for combing,' and both available for a great variety of useful and elegant textile fabrics.1

The fleece of the domesticated varieties of Auchenia (Llama Vicugna) has analogous properties rendering it useful for various manufactures. In all Ruminants the hair is shed annually: this would happen to the wool of Sheep were it not shorn. The Llamas form no exception: the fleece of one in the London Zoological Gardens became ragged and detached in masses in the month of July. Mammals living in cold climes develop a thick undercoat of fur or wool: this is seen in the Musk-bubale, and was the case with the primigenial Elephant2 and Rhinoceros,3 its former associates in high northern latitudes.

The muzzle, the inside of the ears, the sole of the paws, are defended by hair in arctic quadrupeds (e.g. Ursus maritimus). The sole of the foot in the Camel and Dromedary is defended by

In judging of these qualities in wools, it is requisite to test the fineness and elasticity of the fibre, the degrees of imbrication of the scaled surface of the fibre as shown by the microscope, the quantity of fibre developed in a given space of the fleece, the comparative freedom of the fleece from extraneous matters, and the skill and care employed in preparatory processes; such, for example, as that termed scouring the fleece, upon which depends its liability or otherwise to mat at the bottom of the staple. CCXXVIII".

2 CCXL". p. 263.

Ib. p. 351 (Rhinoceros tichorhinus).

hair from the hot sand of the desert.' Nocturnal quadrupeds of hot climates, as, e. g., Lemuridæ, have the soft fur and the longer scantier kind of hair. The northern Wild Boar has an undercoat of fur besides the bristles: in most domestic Hogs the latter alone are developed; and a gland-like body partly surrounds the matrix of the bristle, fig. 485, i. Rhinoceroses and Elephants of tropical latitudes have but one kind of hair, most conspicuous in the young, especially in elevated localities, but almost wholly lost in the full-grown animal. The Hippopotamus, Sirenia, Cetacea, Bimana, are examples of naked Mammals; but on the limited localities where the skin develops such a covering, it is of the mammalian character-hair or bristle. The foetal Whales show the latter on the lip, the adult Elephants and Rhinoceroses on the tail. Human hair, which continues to grow through more or less of life, has distinctions as to localities and length, characteristic of age and sex: it varies in colour from pale yellow to black, and in form from straight to crisp, resembling wool on the head of the Negro variety.

The degree of imbrication of the scaly outer layer of the human hair is such that rubbing one between the thumb and finger pushes the root-end away. Beneath the scales the cortical part of the hair is minutely fibrous; it includes a cellular pith with pigment, upon which the colour of the hair mainly depends. In the minute hairs on the general surface of the body, the pith is wanting. I have observed the hair of the beard to be three-sided, with rounded angles, in transverse section; the hair of the head of the same individual being a full oval in such section.

The general direction of the minute and fine hairs on the human limbs accords with that of the medullary arteries of the long bones, viz. toward the elbow-joint and from the kneejoint. A corresponding disposition prevails in the hairy clothing of the limbs of Quadrumana. In the attitude assumed by an Ape crouching beneath the pelting of a tropical shower, with close-bent limbs, thigh and fore-arm upward, arm and leg downward, the reverse directions of the hairs on the proximal and distal segments will be seen to be such as to act in both as a downward watershed.

The general direction of the hair in swift quadrupeds offers least impediment to forward motion. Some small burrowers, which move backward as well as forward in their long and narrow

xx. vol. iii. p. 243.

2 ESCHRICHT has given ample details of the disposition of the hair in the human fœtus, in ccxxx".

tunnels, would be inconvenienced by such unchangeable disposition of their fur. Accordingly in Moles, Shrews, and Platypi, e.g., the stem of the hair is filamentary, the end broad and flat, and the slender and expanded parts may alternate twice or oftener in the course of the hair, enabling the whole fur to assume any direction in which it may be stroked.

The heat-retaining property of the pilose covering is mainly due to the amount of air it is able to retain. The long curly character of the Sheep's and Llama's fleece is one modification to this end; the swifter Deer and Antelope are not so encumbered; but the hairs composing their thin but close and smooth pelt have a cellular structure which combines lightness with the requisite air-intercepting quality.

In the Horse there is a central point on each flank, whence the hair radiates in a somewhat spiral manner: the corresponding centre in the Giraffe is a little behind the middle of the abdomen, towards the lower part.1

The hide of the larger Ruminants which are exposed to the elements in the prolonged act of grazing is defended by the greasiness of the hair, as may be felt in the recently killed Reddeer or Fallow-deer. The amount of sebaceous matter excreted with the hair in some Antelopes is such as to have suggested a specific name in accordance therewith.2

The varieties of structure of hair are extreme: those of Deer seem almost wholly to consist of cellular pith, the cortex undefinable: the tail-hair of the Horse, and the Pig's bristle, offer the opposite extreme of thickness of cortex and minimum of pith. But these and other modifications demand a special micrography.3 Hairs of some quadrupeds, the Racoon, e. g., in the filamentary productions of the cortical scales, recall the character of the immature down in Birds (vol. ii. p. 237). In some Rodents, the Hare, e. g., several fine hairs project from the mouth of the same sheath as the larger hair. In Mice and Shrews the margins of the cortical scales encompass the hair and project forward or rootward. This free projection is such in some bats that the hair presents the appearance of a succession of ensheathed funnels with their apices backward or outward. The hair of the Sloth is fluted, the crust appearing to be composed of several

The varieties in this respect merit more notice than they have hitherto received. 2 Laurillard's Antilope unctuosa is probably the same species as Kobus Sing-sing of Ogilby.

Brief immersion in sulphuric acid and cleansing with ether are requisite preliminaries for clear and satisfactory microscopic specimens of hairs.

filaments confluent with a common central pith. In the Peccari the pith of the coarse body-hair is crossed by condensed cells like beams strengthening the cortex. The colour of the hair is lost by age in Man, and during the winter season in the annually renewed covering of many arctic Mammals: the endosmotic transfer of their contents from cell to cell of the pith effects this change. The hairs of the Cape-Mole are peculiar for the iridescent tints they reflect, whence its generic name, Chryso

chloris.

The stiffer, thicker kinds of hair' are called bristles:' when these attain unusual length, grow from the lips, cheeks, and other parts of the head, and have the matrix supplied by unusually large nerves, endowing them with tactile or exploratory faculties, they are termed 'whiskers' or 'vibrissæ": those which beset the muzzle of the Walrus attain the thickness and stiffness of spines, and serve, also, mechanical uses.2 The muscles moving vibrissæ have the striped fibre.

a

488

§ 361. Spines.--Over the major part, including the more exposed surfaces, of the skin of the Hedgehogs (Erinaceus, Centetes) spines are developed in such numbers and of such length as to conceal the hairs; they are nearly straight, terminate in a point, and, when fully formed, are smaller at the root than in the shaft. They have a thick, stiff, horny cortex, including a pith of cells arranged in transverse groups, fig. 488, a. The matrix is originally situated beneath the derm, in contact with the strong 'panniculus carnosus;' but section of the skin shows the roots and sheaths of the quills, extending to different depths according to the period of their growth: the newly formed ones are lodged deep, and terminate without contracting, the pulp being large and active, and the cavity containing it of corresponding size; but as the growth of the quill proceeds, the reflected integument forming the sheath gradually shortens and draws the quill nearer the surface; the pulp is at the same time progres'xx. vol. iii. p. 245.

Section of skin, with spines, of Hedgehog: e, section of spine magn.

2 Ib. p. 246.

sively absorbed, and the base of the quill is contracted in diameter, until it adheres to the surface of the derm by a narrow neck, below which is a slightly expanded remnant of the matrix. The disposition of the dermal muscles subserving the spiny armour of Erinaceus europeus, is given at pp. 18, 19, figs. 7 and 8.

In the Porcupine (Hystrix cristata) the spines attain so great a length that they are called quills.' The formative pulp, fig. 489, e, is longitudinally furrowed; to it is due the cellular pith: the capsule or inner layer of the theca is reflected into, or fills, the pulp-grooves, and deposits therein, and continuously around the whole, the horny cortex: the consequent arrangement of crust and pith is such as in transverse section to give the figure, fig. 489. Beneath the matrix is a cavity like a minute' bursa mucosa,' which allows much freedom of motion to the quill when acted upon by the muscle, d, of the sheath, f: a sebaceous gland, h, serves the quill opening into the sheath near the outlet. When the growth is completed, the matrix shrinks, and the same movement to the periphery of the derm takes place as in the spines of the Hedgehog. Thus it happens that when the quills of the Porcupine are violently shaken by the action of the cutaneous muscle, c, the adhesion of some old quills to the derm has been so reduced that they are thrown off.

Section of skin, with matrix and root of quill: i, section of quill, Porcupine.

§ 362. Scales.-Only one genus of Mammal (Manis) offers a covering of scales; and with them are associated hairs. The scales are large, epidermal or horny in tissue, and imbricate or overlapping, with the free border turned backward, vol. ii. fig. 158. The external surface of the derm is raised into large rhomboidal processes, upon which the scales are moulded: beneath the derm is a thick panniculus carnosus,' adapted to draw the integument around the animal as a means of defence, and connected with muscular slips, which erect the scales.