Hair (biology)

“ In the pressing out of worms, I could tell whether there were hairs in them or no, for if the substance came out streight, then there were always hairs, but if bended and bow'd, none.
The make and conformation of these worms, I suppose to be after this manner. When the Root of a hair lying deep in the skin, supplies so much nourishment as to make the hair grow out and appear upon the face, the upper part of the hair by rubbing, or some other violence, comes often to be broke off, the Trunk of it still remaining in the skin. ”

“ The hairy coat of a mammal is composed of individual hairs of varying length, colour and thickness, each being rooted in a tiny pit in the skin and growing from a papilla at its base. As the hair grows, its free end is pushed away from the papilla at the rate of one inch in two months. This is the rate in man’s hair, and it is probably greater in the case of lower mammals on account of the greater importance and physiological activity of their hairy coat than in man’s. ”

“ The Skin and the Hair during the Evolution of the Organism.—In the case of the hair also, the pigment does not remain a constant quantity throughout the different periods of life. Grey hair is a normal sign of the decadence of an organism which has entered upon its involution. As is well known, the hair of the head, the beard, and in general all the piliferous appendages turn white, beginning in the regions where the hair is most abundant, i.e., on the head. In some men, however, the hairs of the beard are the first to turn grey ”

“ Hairs.—As shown in Commission Exhibit No. 666 (p. 587) , a hair consists of a central shaft of air cells, known as the medulla; a cortex containing pigment granules (which give the hair its color) and cortical fusi (air spaces) ; and a cuticle and an outer layer of scales. Unlike fingerprints, hairs are not unique. However, human hairs can be distinguished from animal hairs by various characteristics, including color, texture, length, medullary structure and shape, shape of pigment, root size, and scale size. ”

“ The differences of human hair and hairs generally, from the higher to the lower forms of mammalia, consist only in variations of size and arrangement as regards the cells composing the different parts of the fibre, as well as in a greater or less development of the scales on the covering or external hair surface. Thus, under the microscope, the wool and hairs of various animals, as also even hairs from different parts of the same animal, show a great variety of structure, development, and appearance. ”

“ Hence, while the unborn of these animals still cling to the structural traditions of their ancestors and are covered with hair, the adults are almost hairless. The sartorial habits of human beings and the selective influences of the sexes have had a similar effect on the hairy covering of the human body. Hair exists all over the human body surface, excepting on the soles of the hands and feet, but in a greatly dwarfed condition. It is only on the scalp and on the faces of males, where it is scientifically assisted for purposes of display, that it grows luxuriantly. ”

“ Hair is distributed over all parts of the body, with the exception of the palms of the hands, soles of the feet, and the lips. It grows abundantly upon the head and face, and sparingly upon the trunk and limbs, and according to its location, differences are observed in shape, size, colour, and structure. With reference to the structure, I may observe that a hair has three different modifications of tissue, viz., its centre, which constitutes the medulla, or pith, and is a loose cellulated tissue; that which encloses it forming a greater portion of a human hair called a fibrous tissue ”

“ When the cortical structure of the human hair is examined it is found to be jagged like the teeth of a saw, and it is owing to this imbricated arrangement that hair feels rough to the touch when the hand is passed from point to root. The serrated appearance of hair is produced through the outer layer, or cuticle, being composed of flattened cells, or scales, which overlap each other like the scales of fishes, only they are not so regularly placed. The medulla, also, consists of a number of cells, which can be seen in hair that has been steeped for a time in soda or potash. ”

“ It will be necessary, therefore, to enter into the microscopical structure and development of the mammalian hair. Hair is found in every mammal. The first appearance of a hair is a slight thickening of the stratum Malpighii of the epidermis, the cells taking part in this being {8}elongated and converging slightly above and below. ”

“ The Imperishable Nature of Hair.—The imperishable nature of hair arises from the combination of salt and metals in its composition. In old tombs and on mummies it has been found in a perfect state, after a lapse of over two thousand years. There are many curious accounts proving the indestructibility of the human hair. ”

“ Most mammals are externally clothed with hair, which is a peculiarly modified epidermal process. Each hair, usually cylindrical, is composed of two parts, a central pith containing air, and an outer more solid cortex; each hair rises from a short papilla sunk at the bottom of a follicle lying in the true skin. ”

“ The medulla of the hair contains the pigment granules or coloring matter, which may be of any shade between a light yellow and an intense black. It is this that gives the great variety in color. Generally with old people the pigment is absent, the cells being occupied by air; hence the hair becomes gray or white. The thin, flat scales on the surface of the hair overlap like shingles. Connected with the hair-follicles are small bundles of muscular fibers, which run obliquely in the skin and which, on shortening, may cause the hairs to become more upright, and thus are made to “stand on end.” ”

“ The hair is inclined to grow in certain diseases, especially in consumption, and in old age, and after death; and under these circumstances the hair hardens concomitantly with its growth, and the same duplicate phenomenon is observable in respect of the nails. ”

“ Hairs are only found in the mammalian class, and are divided into the long tactile bristles or vibrissae and the smaller hairs which maintain the warmth of the body. In some animals the hair ot the body is composed of long, stiff hairs, which are probably specialized for protective purposes, and short, soft hairs, which form the fur and keep in the warmth. ”

“ Animals that admit of diversity of colour in the hair admit of a similar diversity to start with in the skin and in the cuticle of the tongue.
In some cases among men the upper lip and the chin is thickly covered with hair, and in other cases these parts are smooth and the cheeks are hairy; and, by the way, smooth-chinned men are less inclined than bearded men to baldness. ”

“ The hair is, in general, thickest where the constitution is strongest, and more glossy and beautiful where the health is most permanent. The ancients supposed the hair to be produced like the nails, the part next the root pushing out that immediately contiguous. But the moderns have found that every hair may be truly said to live and to receive nutriment like other parts of the body. The roots do [70] not turn grey sooner than the extremities, but the whole hair changes colour nearly at the same time, and we have many instances of persons who have grown grey in one night’s time. ”

“ Hence, if a partial loss of hair was esteemed ornamental by our ape-like progenitors, sexual selection, operating age after age, might result in relative nakedness. “The faces of several species of monkey and large surfaces at the posterior end of the body have been denuded of hair; and this we may safely attribute to sexual selection.” The beard of the male, and the great length of the hair of the head in some races, especially seem due to this cause. ”

“ But it is most especially noticeable in mammals, which have frequently the under side almost entirely bare of hair, while the back is covered with a copious crop. Now, it would seem as though this scantiness of natural clothing on the under side were due to long continued pressure against the ground, causing the hair to be worn away, and being hereditarily transmitted in its effects to descendants. We are, therefore, led to inquire whether all parts of the mammalian body which come into frequent contact with other objects are specially liable to lose their hair. ”

“ On the sides of the body the hairs are coloured in the same way, excepting that the white portion is more extended, and is followed by a rich yellow-brown, shaded into black as it approaches the apex of each hair. ”

“ The adjective by which I characterize this system, is derived from the latin substantive which signifies the organs of which it is composed. Hair is found less generally upon man than upon most other animals. It forms upon them a kind of covering external to the skin, which, lessening in part the contact of external bodies, makes the cutaneous animal sensibility perform a less important part, and establishes less numerous relations between these bodies and them. ”

“ It does not seem probable, to me at least, that a naturally hairy species would entirely divest itself of its hair through sexual selection, especially as the first steps of such a process could hardly fail to render it a mongrel-looking and miserable creature; but it seems natural enough that, if the original impulse was given by a physical denudation, the influence of sexual selection would rapidly strengthen and complete the process. Indeed, if a hairy animal once began losing its hair, the only beauty which it could aim at would be that of a smooth and shiny naked black skin. ”

“ 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. ”

“ Every hair has a root, just as a tree has, and through this root it receives its nourishment. As the vessel [Pg 252] which feed a plant are always proportionate to the size of the plant itself, how fine must be those vessels which form the roots of the hair, being in proportion to the size of the hair, which is in itself so small that the eye cannot see its structure? The hair is, in fact, an animal plant, growing upon the body in much the same manner that plants grow upon the surface of the earth. ”

“ The colour of the skin and hair, and the odour emitted by the glands of the skin, are said [812] to be connected, even in the same race of men. Generally the hair varies in the same way all over the body in length, fineness, and curliness. The same rule holds good with feathers, as we see with the laced and frizzled breeds both of fowls and pigeons. ”

“ The burnt Ashes of little Froggs applyed cures the falling of the hair, called Alopecia. The burnt Ashes of Goats Dung mixt with Oyl, anointed, multiplys the Hair. The Ashes of a Goat's Hoof mixed with Pitch healeth the Alopecia. The Ashes of Bees mixt with Oyl, or the ashes of Southernwood mixt with old Oyl, causeth hair to grow. A Lee of the Ashes of Ivie-tree-Bark causeth hair grow yellow. The Blood of a shell Crab anointed, breeds much hair. But the Blood of a Bat, or a little Frog, the powder of a Swan's Bones, or the Milk of a Bitch hinders the growing of the hair. ”

“ As for hair, men differ in this themselves at different ages, and also from all other kinds of animals that have hair. These are almost all which are internally viviparous, for even when the covering of such animals is spiny it must be considered as a kind of hair, as in the land hedgehog and any other such animal among the vivipara. Hairs differ in respect of hardness and softness, length and shortness, straightness and curliness, quantity and scantiness, and in addition to these qualities, in their colours, whiteness and blackness and the intermediate shades. ”

“ In creatures with vibrissæ, however, and in those quadrupeds whose whiskers are tactile organs, it can hardly be doubted that the feeling is projected out of the root into the shaft of the hair itself. We ourselves have an approach to this when the beard as a whole, or the hair as a whole, is touched. ”

“ That this is its most important function, is well shown by the manner in which the hairs are disposed so as to carry off the water, by being invariably directed downwards from the most elevated parts of the body. Thus, on the under surface the hair is always less plentiful, and, in many cases, the belly is almost bare. The hair lies downwards, on the limbs of all walking mammals, from the shoulder to the toes, but in the orang-utan it is directed from the shoulder to the elbow, and again from the wrist to the elbow, in a reverse direction. ”

“ The hair is a dry fume (fumus siccus) , escaping from the body through the pores of the scalp and condensed by contact with the air into long, round cylinders. It increases rather by accretion than by internal growth, and its color depends upon the humors. Thus red hair arises from unconsumed blood or bile; white hair, from an excess of phlegm; black hair, from the abundance of black-bile (melancholia) , etc. The use of the hair is for ornament, for protection and for the distinction of the sexes. ”

“ Hair is to the human aspect what foliage is to the landscape; and, whenever pen or pencil is guided by poetic feeling or good taste, it lingers with admiration and delight amid the shadows and glossy silken sheen—the ever-varying tints, and waving, wanton loveliness of sunny, luxuriant hair. ”

“ Certainly this is the case with the beard, whose absence in women shows it to be of no utility, and whose presence in man is in accord with the many structures in male animals apparently due to this form of selection.
Darwin has pointed out and explained a very curious peculiarity of the hair in man, which is absolutely inexplicable except on the theory of descent. This is the fact that the hairs on man's arms are directed toward the elbow from above and below, thus growing in opposite directions on the upper and lower arms. ”