The latter group are known as the arrectores or erectores pilorum. These follicular muscles not only have fixed points of attachment to the papillary layer of the corium and fixed points of insertion into several hair-follicles at a level just above the apex of the hair-papillae, but by means of elastic fibers which surround and mingle with them throughout their length and at their ends form tendons, they are directly attached on every side to the elastic framework of the corium. Their direction is oblique. The direction of the hair being at a less oblique angle, a powerful contraction of these muscles pulls the hair into a more erect position. In some of the lower animals this effect may be seen in a marked degree. The more important effects which follow the ordinary contraction of the oblique muscles of the corium are the expulsion of sebum by compression of the sebaceous glands, a lessened circulation of blood in the papillary layer, and diminished perspiration from the general tension of the upper part of the corium. The compression exerted upon the skin in this way sometimes produces an apparent roughening of the surface (cutis anserina or goose flesh). A general effect is to prevent loss of bodily temperature. Therefore, one of the functions of the oblique muscles of the skin is the regulation of temperature. External cold stimulates their contraction and external heat promotes their expansion.
PIGMENT
The shade of color of the skin is due partially to the degree of vascularity and distention of the blood-vessels in the corium. In other words it depends upon the quantity of blood circulating in the skin. The other element is the amount of staining in the cells of the lower strata of the rete, most pronounced in the nuclei and due to the deposit of fine granules of pigment (melanin) in the cell cavity. The amount of coloring matter in the layers of the epidermis is influenced somewhat by exposure to the sun, habits, climate, racial and other differences.
Pigmentation of the greater part of the skin, in the white race, is slight and limited to a uniform pigmentary deposit in the lower rete cells. The deeper colored portions of the skin of the white race such as the scrotum and areolar of the nipple, and the general integument of the colored races, are produced by a wider or deeper pigment staining and deposit in the prickle cells and their nuclei. In the negro pigmentation ascends to the granular layer and a dark coloration of the skin results. There is never any real pigmentation of the corneous layer of the epidermis and only in abnormal conditions is it found in the corium. The source of the pigment in the skin is undetermined, but it is probable that the pigment is derived from the subepidermal structures and in some way is originally obtained from the blood itself.
SWEAT-GLANDS
(Coil-glands; Sudoriparous glands; Glandulae sudoriferae; Glandulae glomiformes)
Coil-glands (T, Fig. 1) may be observed in the fifth month of fetal life and originate from in growing of the rete cells in the form of conic epithelial processes into the corium. In the course of development the central part liquifies forming a tube. These glands are present in great numbers in all parts of the skin except the colored border of the lips, glans penis, inner surface of the prepuce and the clitoris. They are most numerous in the palms and soles, where, according to Krause, they number nearly 3,000 to the square inch. They vary in size according to location being largest in the axillary and anal regions. The average length of a straightened tube is about a quarter of an inch, and it is estimated that the total length of these tubes in the normal adult skin is upward of nine miles.
Sweat-glands originate in the subcutaneous tissue and consist of a simple tube coiled several times upon itself forming an avoid convoluted body with a blind end in the central or outer part of the coil, and an excretory duct. The latter is simply a continuation of the lower tube somewhat altered. It traverses the corium straight upward between the papillae, passes through the rete in a less regular manner and through the corneous layer in a wavy or spiral manner and opens upon the surface in a funnel shaped aperture, the so-called sweat-pore. Unna believes that the true duct ends at the surface of the corium and the remaining portion of the tube outward is a common outlet for exudations from the interstices of the epidermis and for the sweat. The sudoriparous glands are simple in structure. The outer coat is continuous with the basement membrane of the corium; the middle or epithelial coat is continuous with the deeper layers of the stratum mucosum; the inner coat or lining is a delicate cuticle. The sweat-glands are each surrounded by a sheath of connective tissue and fat cells, which support and hold the tubes in position.
SEBACEOUS GLANDS
(Oil-glands; Hair-follicle glands; Glandulae sebaceae; Glandulae sebiferae)
Sebaceous glands (S, Fig.1) are first noted in the third or fourth months of fetal life, appearing as buddings from the external root-sheath of the hair- follicle. These projections consist of epithelial cells which by multiplication and further downward growth, form the gland. They are richly supplied with blood-vessels, being surrounded by a network of capillaries. They appear first in the skin of the eyebrows and forehead, like the hairs, thence spread over the trunk, finally reaching the extremities. Oil-glands are simple or complex, racemose structures lined with round-cell epithelia. By a process of slow fatty degeneration and rupture of the cells lining each acinus, their secretion called sebum is produced. The ducts leading from these glands are short and end in the hair-follicles, or open directly on the surface. These glands are to be found in the corium of almost any part of the body surface except the palms, soles and dorsum of the third phalanges. According to their distribution they are divided into three groups.
The first class are found in the skin of the hairy part of the body and are very abundant, being connected with the hair-follicles into which they discharge. Strictly speaking they are appendages of the hair and the hair- follicles, being sometimes known as “glands of the hair-follicles.” The second class is found upon the so-called non-hairy surfaces such as the face and upper portions of the trunk and extremities. This group includes the large and complex glandular structures to which the lanugo or fine hairs seem accessory. The ducts of these glands open directly on the cutaneous surface. The third group are limited in number being found in the red border of the lips, the areola of the nipples, labia minora and vestibule of the female, and on the internal surface of the prepuce and corona in the male. They are not connected with the hair- follicles, open directly on the surface and might be designated “glands of the mucous orifices.”
Structurally sebaceous glands consist of the secretory portion and the duct which empties between the surface of the hair and its inner root-sheath. The various lobules empty into a common glandular cavity containing fat-globules, crystals and epithelial debris, which constitute what is known as sebum, or sebaceous matter. It is not now believed that smegma, found about the glans penis and inner side of the prepuce, is a product of the sebaceous glands but rather an exfoliation of the corneous layer of the epidermis. Possibly both factors may be causal in its production.
HAIRS
Hairs (H, Fig.1) are elongated, cylindric, horny formations derived from the epidermis and are obliquely planted in depressions in the corium known as hair- follicles or hair-sacs. Ordinarily one hair only occupies each hair-follicle but in rare instances, two or even three hairs have been observed in a hair- follicle. Hairs of some degree, no matter how minute, are found on all body surfaces except the palms, soles, dorsum of the distal phalanges of the hands and feet, lips, glans penis and inner surface of the prepuce. For convenience they may be divided into three classes: (1) the fine downy or lanugo hairs found upon the general surface; (2) short, strong or bristly hairs such as the eyebrows or eyelashes and those in the nares and outer auditory canal; (3) the long, softer hair of the scalp, beard, axillae and genital regions. Hairs vary in different individuals, nationalities and types, due, as During has pointed out, mainly to the degree of straightness or curl, caliber, length and color. While abundant, hairs vary considerably in number, the average growth on the scalp being about 1,000 to the square inch, approximately about 120,000 to the entire region.
The color of the hair is due to the varying amount of pigment-granules and diffused pigment present in the cortical and medullary portions of the hair and to the presence of air, usually in the form of air-vesicles. The latter element plays an important part in the physiology of white, gray and blond hair. The degree of pigmentation usually corresponds with that of other parts of the skin. It varies widely in different races and individuals and, to some extent in the same person under changed states of nutrition caused by rapidly or slowly acting influences on the tropic nerves.
American homeopath, he directed several hospitals in New York.
Professor of dermatology.
Served as Lieut. Colonel during the 1st World War.
See his book online: American homeopathy in the world war