influences. Still more strikingly is this shown by the blackness of the Melanian aborigines of New Guinea, Australia, and Tasmania, retained from the sixth to the forty-third degree of south latitude; and especially of those of the outlying islands in proximity with others inhabited by the olive-brown Polynesians, whose complexion prevails from lat. 12° S. to 46° S. (New Zealand). But the most instructive example of the closer relationship of tint to race than to climate is afforded by the aborigines of the New World, which hold nearly the same depth of copper-brown or reddish tint, latitudinally from Tierra del Fuego to Hudson's Bay, and longitudinally from the Atlantic to the Pacific. The contrast between the South American Indians and the African Negroes would seem to be decisive against the hypothesis of degrees of solar influence being the causes of degrees of darkness of complexion.

But there is an element in the problem which ought to be taken into consideration, viz. time.' If Africa be an older continent than South America, its aborigines may have been subjected to solar influences through a longer series of generations. We know not the extent of such series; some may deem that were the intertropical South American Indians subject to a vertical sun during the long ages of Africa's emersion, they would acquire a darker complexion.

Climate, however, depends on other influences than sunshine. Degrees of moisture, and whatever influences cause a contrast or gradation of seasons, &c., may have their effects upon complexion. Filthy habits, foul air, and bad food, affecting biliary and other secretions, have their share in darkening the skins or sallowing the complexions of the Esquimaux, Fins, and Laps, e.g. as compared with the cleanlier and more healthily living and better nourished Scandinavians residing some degrees further from the pole. But assuming, as the general result of the above survey of human complexions, that such complexions do, in the main, show a certain dependent relationship on solar light and heat, and postulating the effect of long periods of such subjection, we might then be led to conclude the darkest of the intertropical and warm temperate peoples to be the oldest; that the Melanians, scattered on islands to the east of the Indian Ocean, inhabit relics of a continent as old as, perhaps older than, Africa; and that the lighter-tinted races on intercalated or contiguous portions of dry land are subsequent immigrations or derivatives from lands less affected by solar influences. On this hypothesis it may be inferred that the deepest-tinted races

existing in the islands of the Malayan Archipelago are the oldest inhabitants of such-those most entitled to be termed aborigines. The Hindoos, by the same pigmental test, would be deemed older than the Parsee or Mahometan natives of Hindostan, as history, indeed, testifies. In extra-tropical latitudes, human generations may have succeeded each other for the same duration of time as in tropical ones, without further deepening or development of pigment than such diminishing influence of the sun may effect. Such peoples, migrating to tropical countries, may long maintain their inherited complexions; just as the black races migrating to extra-tropical latitudes long retain the tint inherited from forefathers in whom it has been established primarily by the requisite continuance of exposure to extreme solar heat and light.

§ 359. Callosities.-The epiderm, besides forming the firm and more or less insensible outer protection of the derm, acquires unusual thickness at certain parts in different mammals. It forms callosities over the sternum of the Camel and Dromedary, and upon the parts of the joints (carpal and rotular) on which these useful beasts of burden kneel. It defends the broad back of the penultimate phalanges of the fingers of the knuckle-walking Apes, the ischial tuberosities of most lower Catarhines, and the prehensile surface of the tail in many Platyrhines.

In the Equide there are callosities on the inner surface of the limbs, which, however, are more dermal than epidermal. In the Horse, on the inner side of the fore-leg, a little above the carpus (fore-knee' Hippotomy), and on the inner side of the hind-leg. a little below the tarsus' (hock-joint, Hippotomy), is a naked protuberance of a soft horny consistence, about the size of a chestnut, and called châtaigne' by the French veterinarians. Behind the metacarpo-phalangeal joint is a similar but smaller horny tubercle, called the 'ergot,' or spur. The Ass has not the 'châtaigne' on the hind-leg; but there is the vestige of one on the fore-leg, situated there as in the Horse; it consists of a patch of black skin devoid of hair, but not horny. There is a similar trace of the spur (ergot) behind the metacarpo- and metatarso-phalangeal joints. The Zebra resembles the Ass in these respects: the homologue of the fore-leg callosity is a patch of black naked skin about 3 inches long and 3 inches broad; the callosities behind the metacarpo-tarso-phalangeal joints are like those of the Ass.

§ 360. Hair.-The cutaneous clothing characteristic of the Mammalian class is hair.' It consists of unbranched filaments of epidermal material, usually composed of pith' and 'crust,'

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and in which are distinguished the root,' the 'stem,' and the 'point.'

487

The root is softer and lighter in colour than the stem,' is contained in a canal of the skin or sheath, fig. 487, e, and expands at the implanted end into the knob.' This part during the growth of the hair has a conical cavity inclosing the bulb,' ib. f, which forms the 'pith;' from its base there is reflected upon the knob' a capsular layer of cells which forms the crust;' this layer is continued to near the outlet of the sheath; it consists of two or more layers of cells, the outermost of which have generally lost their nuclei.’ The proper tunic of the sheath is 'derm,' lined by epiderm continuous with the cuticle, which accordingly, when shed, usually brings away the hairs. In the dermic part there is a vascular and a hyaline layer; the latter ceasing with the capsular part of the hair's matrix.

Two sebaceous glands, ib. h, usually open into the hair-sheath; and one or more delicate muscles, ib. 9, of unstriped fibre, pass from the harder superficies of the derm to be inserted

into the capsule beneath the glands; these are mainly concerned in raising the hairs.

Hairs, like teeth, are of two kinds as regards growth; one temporary, the other persistent. The former are shed and succeeded by new hair, usually once a year; the latter have persistent bulbs and perennial growth. The body-hair of the Horse is an example of the first kind, the hair of the mane and tail of the second kind. In many Mammals there are two kinds of hair, according to form, length, and structure; one short, fine, more or less curled, and mostly hidden by the longer, coarser, and straighter kind, which is sometimes called the external coat, albeit the roots sink deeper into the derm than do those of the internal coat, usually called 'fur.'

These two kinds of hair-inner and outer-are most distinctly as well as abundantly shown in arctic and aquatic quadrupeds, (ermine, sable, beaver, and the seal-tribe), especially in the young state, when the heat-forming power is weak. In some species of

The contrast is striking in the hair of the Ornithorhynchus, in which the brown tint is confined to the expanded terminal part of the hair.

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.'

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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 Ovis Vignei, the Ovis Ammon of Central Asia, and the Ovis 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.'

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

1 xx. vol. iii. p. 243.

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