SKIN DISEASES 121 applied to describe an accumulation on the skin of the normal sebaceous secretion mixed up with dirt and form- ing scales or a distinct incrustation. On the head, where it is commonly seen, it may interfere with the nutrition of the hair and cause partial baldness. A form of this disease occurs in young infants. The main treatment is local, consisting in thorough cleansing of the parts. The crusts may be softened with oil and the affected skin regularly washed with soft soap and rectified spirit. The sebum frequently accumulates in the sebaceous ducts, giving rise to the minute black points so often noticed on the face, back, and chest in young adults, to which the term comedones is applied. A form of this disorder, but of larger size and white appearance, is termed milium. These affections may to a large extent be prevented by strict attention to ablution and brisk friction of the skin, which will also often remove them when they begin to appear. The retained secretion may be squeezed out or evacuated by incision and the skin treated with some simple sulphur application. Acne is an eruption produced by inflammation of the sebaceous glands and hair follicles. It may occur in con- nexion with the preceding or independently, and shows itself in the form of red pimples or papules which may become pustular and be attended with considerable surrounding irritation of the skin. This affection is like- wise most common in early adult life, and occurs on the chest and back as well as on the face, where it may, when of much extent, produce considerable disfigurement. It is apt to persist for months or even years, but usually in time disappears entirely, although slight traces may remain in the form of scars or stains upon the skin. Eruptions of this kind are sometimes produced by the continued internal use of certain drugs, such as the iodide or bromide of potassium. The treatment is similar to that for the previous affection, viz., brisk friction of the skin, short of producing irritation, and the application of a sulphur lotion or ointment. Attention to the general health by suitable diet, tonics, exercise, &c., is a necessary adjuvant. A variety of this malady, to which the name acne rosacea is given, is a more severe and troublesome disorder than that already mentioned. It is characterized by great redness of the nose and cheeks, accompanied with nodular enlargements on the surface of the skin, which produce marked disfigurement. Although often seen in persons who live too freely, it is by no means confined to such, but may arise in connexion with disturb- ances of the general health, especially of the function of digestion, and in females with menstrual disorders. It is apt to be exceedingly intractable to treatment, which is here too, as in the preceding form, partly local and partly constitutional. Of internal remedies preparations of iodine and of arsenic are sometimes found of service. Molluscum contagiosum belongs to this class of skin diseases. It consists of an enlargement of the sebaceous glands and occlusion of the ducts, and is seen most commonly on the face, body, or hands in children, or on the breasts in women. It is said to be contagious, but it is a rare form of skin disease. II. DISORDERS AFFECTING NUTRITION. (1) Hypertro- phies. A corn (davus) is a local thickening of the skin, generally occurring on the toes. There is hypertrophy of the epidermis, and in the centre of the corn there is usually a still denser mass, which, pressing down upon the subjacent sensitive true skin, causes pain and may give rise to inflammation and suppuration in the part. When situated between the toes the corn is softer than when on the free surface of the foot. The treatment consists in maceration of the hardened skin and the use of the knife or strong caustics. Salicylic acid combined with ether and collodion, painted over the part, is said to be useful in the case of soft corns. A wart (verruca] is an excrescence from the surface of the skin due to hypertrophy of the papillary layer of the cutis and of the epidermis. This form of growth may also occur on mucous membranes. Warts occasionally disappear spontaneously, or they may be excised, or care- fully touched with some strong caustic acid or alkali. Ichthyosis or xeroderma consists of a general thicken- ing of the whole skin and marked accumulation of the epidermic elements, with atrophy of the sebaceous glands, giving rise to a hard, dry, scaly condition. It generally first appears in infancy, and is probably congenital. It differs in intensity and in distribution in different cases, and is generally little amenable to any but palliative remedies, such as the regular application of oily sub- stances, although it is not a fatal malady. For elephantiasis Arabum, see vol. viii. p. 126. (2) Atrophies. The chief of these relate to the hair. Canities or whitening of the hair consists in the non- formation of the pigmentary matter which is normally present in the substance of the hair, and occurs generally as a slow senile change. It may, however, take place prematurely, in which case it is often hereditary ; or it may be associated with degenerative changes taking place in the system. It is occasionally seen to occur temporarily in very young persons in connexion with some defective condition of the general health. Its development suddenly has not unfrequently been observed as the result of some strong mental emotion. Alopecia, or baldness, is the loss of hair, which is most commonly a senile change and irremediable, or on the other hand may be premature, occurring either heredi- tarily or in connexion with some previous constitutional morbid state (e.g., after fevers or other blood poisons), in which latter case it may be only, although not always, temporary. It appears to depend upon atrophic changes affecting the hair follicle, including obliteration of the capillary vessels, the result of which is that strong hairs cease to be produced, and only feeble, short, and thin hair (lanugo) is formed, which soon falls off and is not repro- duced. Usually the whole skin of the hairy scalp under- goes thinning and other atrophic changes as well as the hair follicle. Sometimes the loss of hair occurs in distinct circular patches (alopecia areata), which tend to spread until the whole scalp is denuded. The treatment of temporary or premature baldness bears reference especially to any known conditions affecting the general health ; and tonics, baths, and other means to promote a vigorous skin function are useful. Stimulating liniments containing spirits and cantharides, the regular cleansing and moderate brushing of the parts, the application to the scalp of the constant current of electricity, and various other remedies appear to be of service in promoting the growth of hair. (3) New Formations. (a) Lupus is a disease character- ized by the formation in the skin of tubercles or nodules consisting of new cell growth which has no tendency to further development, but to retrograde change, leading to ulceration and destruction of the skin and other tissues in which it exists, and the subsequent formation of per- manent white scars. Lupus vulgaris is most commonly seen in early life, and occurs chiefly on the face, about the nose, cheeks, ears, &c., but it may also affect the skin of the body or limbs. It first shows itself in the form of small, slightly prominent nodules covered with thin crusts or scabs. These may be absorbed and removed at one point, but they tend to spread at another. Their dis- appearance is followed by a white permanent cicatrix. The disease may be superficial in which case both the
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