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rest of the derma. Secondly.-Around the nipple of the white woman, the superficial layer of the derma presents the same granular appearance as the pigmental membrane of the coloured races. And thirdly. -The pigmental layer around the nipple of the white woman is placed, as in the coloured races, under the two cuticles.

Fig. 40.

Modern histologists consider the epidermis to be composed of a series of flattened, scale-like cells, epidermic cells, which, when first formed, are of a spheroidal shape; but gradually dry up. These form various layers. According to M. Raspail,' it

Vertical Section of the Cuticle from the consists of a collection of vesicles de

Scrotum of a Negro.

a. Deep cells, loaded with pigment. b. Cells

at a higher level, paler and more flattened. c. Cells at the surface, scaly and colourless as

in the white races.-Magnified 300 diameters. Fig. 41.

Section of the Skin.

prived of their contents, closely applied together, dried, and thrown off in the form of branny scales. regards it as the outer layer of the

corium.

He

The epidermoid tissues have the simplest structure of any solids.

Analysis has shown, that the chemical constitution of the membranous epidermis of the sole of the foot is the same as that of the compact horny matter of which nails, hair, and wool are composed.

2. The corpus or rete mucosum, rete Malpighii, mucous web, is generally regarded as constituting the next layer. It was considered by Malpighi to be mucus, secreted by the papillæ, and spread on the surface of the corpus papillare, to preserve it in the state of suppleness necessary for the performance of its functions. In this rete mucosum, the colouring matter of the dark races seems to ex1. Cuticle, showing the oblique laminae of which it is composed and the imbricated dis- ist. It is black in the African, or position of the ridges upon its surface. 2. Rete mucosum. 3. Two of the quadrilateral rather in the Ethiopian; and copperpapillary masses seen in the palm of the hand coloured in the mulatto.2 Gaultier3 minute conical papillæ. 4. Deeper layer of considers it to be composed of four the cutis, the corium. 5. Adipose vesicles; showing their appearance beneath the micro- layers; but this notion is not admitscope. 6. Perspiratory gland with its spiral duct, as seen in the palm of the hand or sole ted by anatomists, and scarcely conwith a straighter duct, such as seen in the cerns the present inquiry. M. Brescalp. 8. Two hairs from the scalp, enclosed schet affirms, that there is a special "chromatogenous or colorific apparatus," for producing the colouring

[graphic]

or sole of the foot; they are composed of

of the foot. 7. Another perspiratory gland

in their follicles; their relative depth in the skin preserved. 9. A pair of sebaceous glands opening by short ducts into the follicle of the hair.

Chimie Organique, p. 245, Paris, 1833.
Sir E. Home, Lect. on Comp. Anat., v. 278.

3 Recherches Anatomiques sur le Système Cutané de l'Homme, Paris, 1811.

matter, composed of a glandular or secreting parenchyma, situate a little below the papillæ, and presenting special excretory ducts, which pour out the colouring matter on the surface of the derma.

Modern observers deny, that there is any such distinct layer. Some regard it as the deepest or most recently formed part of the cuticle. M. Flourens' considers, that the term corpus mucosum ought to be replaced by that of pigmental apparatus,-appareil pigmental; and that the term rete or corpus reticulare in the signification of a special network situate between the derma and the two cuticles, ought to be banished from anatomy. The nature of the pigment will be referred to hereafter, under SECRETION.

The rete mucosum is considered to be the last formed portion of the cuticle.

Fig. 42.

3. The corpus papillare, or what M. Breschet calls the "neurothelic or mammillary nervous apparatus," is seated next below the rete mucosum. It consists of a collection of small papillæ, formed by the extremities of nerves and vessels, which, after having passed through the corium beneath, are grouped in small pencils or villi on a spongy, erectile tissue. These pencils are disposed in pairs, and, when not in action, are relaxed, but become erect when employed in the sense of touch. They are very readily seen, when the cutis vera is exposed by the action of a blister; and are always evident at the palmar surface of the hand, and especially at the tips of the fingers, where they have a concentric arrangement. These villi are sometimes called papillæ. They are, in reality, prolongations of the skin; and consequently-as M. Flourens has re- fied 35 diameters. marked "the pretended corpus papillare, taken as a body, apart and distinct from the derma, is but an idle

name."

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Papillæ of the palm, the Cuticle being detached.-Magni

4. The corium, cutis vera, derma, true skin, is the innermost layer of the skin. It consists of a collection of dense fibres, intersecting each other in various directions; and leaving between them holes for the passage of vessels and nerves. It forms a firm stratum, giving the whole skin the necessary solidity for accomplishing its various ends; and consists chiefly of gelatin ;-hence it is used in the manufacture of glue. Gelatin, when united with tannic acid, forms a substance which is insoluble in water; and it is to this combination that leather owes the properties it possesses. The hide is first macerated in lime-water to remove the cuticle and hairs, and leave the corium or gelatin. This is then placed in an infusion of oak bark, which contains tannic acid. The tannic acid and the skin unite; and leather is the product.

These four strata constitute the skin, as it is commonly called; yet all are comprised in the thickness of two or three lines. The cutis vera is united to the structures below by areolar tissue; and this, with

Op. cit., p. 38.

2 Op. cit., p. 38.

These

the layers external to it, forms the common integument. In certain parts of the body, and in animals more particularly, the cutis vera is adherent to muscular fibres, inserted more or less obliquely. form the muscular web, mantle or panniculus carnosus. The layer is well seen in the hedge-hog and porcupine, in which it rolls up the body, and erects the spines; and in birds, raises the feathers. In man, it can hardly be said to exist. Some muscles, however, execute a similar function. By the occipito-frontalis, many persons can move the hairy scalp; and by the dartos the skin of the scrotum can be corrugated. These two parts, therefore, act as panniculi carnosi.

In the skin are situate numerous sebaceous follicles or crypts, which separate an oily fluid from the blood, and pour it over the surface to lubricate and defend it from the action of moisture. They are most abundant, where there are folds of the skin, or hairs, or where the surface is exposed to friction. We can generally see them on the pavilion of the ear, and their situation is often indicated by small dark spots on the surface, which, when pressed between the fingers, may be forced out along with the sebaceous secretion, in the form of small worms. By the vulgar, indeed, these are considered to be worms. The follicular secretions will engage attention hereafter.

b

Fig. 43.

The consideration of the hair belongs naturally to that of the skin. The roots are in the form of bulbs; taking their origin in small follicles or open sacs, hair follicles, formed by the inversion of the cutis, and lined by a reflexion of the epidermis. Around each bulb there are two capsules, the innermost of which is vascular and a continuation of the corium. The hair itself consists of a horny, external covering, and a central part, called medulla or pith. When we take hold of a hair by the base, with the thumb and forefinger, and draw it through them from the root towards the point, it feels smooth to the touch; but if we draw it through from the point to the root, we feel the surface rough; and it offers considerable resistance. It is, therefore, concluded, a. Transverse section of a hair of the that the hair is bristled, imbricated or head, showing the exterior cortex, the me- consists of eminences pointing towards and a central space filled with pigment. its outer.extremity, and it is upon this where no aggregation of pigment in the structure, that the operation of felting is axis exists. c. Longitudinal section, without a central cavity, showing the imbrica- dependent-the hairs being mechanically the pigment in the fibrous part. d. Sur entangled and retained in that state by face, showing the sinuous transverse lines the inequalities of their surface. Certain d'. A portion of the margin, showing their observers have, however, failed in detecting this striated appearance by the aid

d

11

Sections of Hair.

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dulla or pith with its scattered pigment,

b. A similar section of a hair, at a point

tion of the cortex, and the arrangement of

formed by the edges of the cortical scales.

imbrication.-Magnified 150 diameters. (Todd and Bowman.)

of the microscope; and Dr. Bostock' affirms, that he had an opportunity of viewing the human hair, and the hair of various kinds of animals, in the excellent microscope of Mr. Bauer, but without being able to observe

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it. Bichat, however, and more recently, Dr. Goring,3 and most histologists, have assigned this as their structure; and the author has had repeated opportunities for confirming it with his own admirable microscope, made by Smith, of London.

Modern observers believe, that, as in other structures, growth takes place from cells, which are a modification of those of the epidermis. The primary cells become elongated, and generate within themselves fasciculi of fibres or secondary cells, which interlace to form the hair cylinder. The walls of these fibre-cells are at first soft and permeable; and the lower part of the hair, which is composed of them, seems to admit the passage of fluid without much difficulty. At a short distance from the base, the horny character of the hair, caused by the deposit of horny matter in the interior of the fibres, becomes apparent. "There is then, at the base, a continual formation of soft fibrous tissue, by which the length of the cylinder is increased; whilst at a short distance above it, there is a continual consolidation of this (as it progressively arrives at that point) by the deposit of a peculiar secretion in its substance."4

Physiology, p. 52, 3d edit., Lond., 1836.

Anat. Général., tom. iv., § 2.

$ Journal of Science, New Series, vol. i. 433. Carpenter, Human Physiology, $ 637. Lond., 1842.

The colour of the hair is different in different races and individuals. By some, this is considered to depend upon the fluids contained in the pith. M. Vauquelin' analyzed the hair attentively, and found it to consist chiefly of an animal matter, united to a portion of oil, which appeared to contribute to its flexibility and cohesion. Besides this, there is another substance, of an oily nature, from which he considers the colour of the hair is derived. The animal matter, according to that chemist, is a species of mucus; but other chemists believe it to be chiefly albumen. Vauquelin found, that the colouring matter is destroyed by acids; and he suggests, that when it has suddenly changed colour and become gray, in consequence of any mental agitation, this may be owing to the production of an acid in the system, which acts upon the colouring matter. The explanation is hypothetical, and is considered, and characterized as such by Dr. Bostock; but it must be admitted, that the same objection applies to the view he has substituted for it. He conceives it "more probable that the effect depends upon a sudden stagnation in the vessels, which secrete the colouring matter; while the absorbents continue to act, and remove that which already exists." There is, however, no more real evidence of "stagnation of vessels" than there is of the formation of an acid. Our knowledge is limited to the fact, that a sudden and decided change in the whole pileous system may occur after great or prolonged mental agitation.

"My hair is gray, but not with years,

Nor grew it white in a single night,

As men's have grown from sudden fears."

Byron's "Prisoner of Chillon."

"Danger, long travail, want and wo,

Soon change the form that best we know:

For deadly fear can time outgo,

And blanch at once the hair.

Hard toil can roughen form and face,

And want can quench the eye's bright grace,
Nor does old age a wrinkle trace

More deeply than despair."

Scott's "Marmion."

It is stated by M. De Lamartine,3 that such a change occurred in a single night to the queen of Louis the 16th-the unfortunate Marie Antoinette-when the royal party was arrested at Varennes, in 1791.

But a similar, though more gradual change, is produced by age. We find some persons entirely gray at a very early period of life; and, in old age, the change happens universally. It is not then difficult to suppose, that some alteration in the nutrition of the hair may supervene, resembling that which occurs in the progress of life. Dr. Bostock doubts the fact of such sudden conversions; but the instances are too numerous for us to consider them entirely fabulous. Still, it is difficult to comprehend how parts, which, like the extremities of the hair, are

1 Annales de Chimie, tom. lviii. p. 41, Paris, 1806.

For many such cases see M. E. Wilson, a Practical Treatise on Healthy Skin, p. 95. London, 1845.

3 "La reine ne dormit pas. Toutes ses passions, de femme, de mère, de reine, la colére, la terreur, la desespoir, se livrèrent un tel assaut dans son âme, que ses cheveux, blonds la vieille, furent blancs le lendemain."-Histoire des Girondins, i. 116. Paris, 1847.

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