The secondary or consecutive lesions of the skin, six in number, are: (1) Excoriatians (abrasions, scratch-marks), variously sized' and shaped areas, representing loss of superficial cutaneous tissue, the result of mechanical vio lence. (2) Fissures, linear cracks or wounds of variable size, involving the epidermis, or the epidermis and corium, due to disease or external injury. These are seen not infrequently in the palms or about the angles of the mouth, when from any cause the parts have become inelastic.
(3) Scales, dry, laminated, masses of epider mis which have separated from the un derlying tissue as the result of some morbid process. They may lie in masses upon the skin, or be constantly exfoliated from the surface. Variations occur in color, consistency and form.
(4) Crusts (scabs), dried, effete masses of ex udation, mixed with epithelial debris, varying in size, shape and color. (5) Ulcers, variously sized and shaped losses of cutaneous substance, the result of preceding disease. In this form of lesion, differences are found in size, outline, depth, condition of floor, margins, etc. A famil iar example is the leg ulcer m old people. (6) Scars, new connective-tissue formations replac ing loss of substance in the corium or deeper tissues.
Besides recognizing the presence and detailed appearance of the lesions upon the skin, the diagnostician must also note their distribution upon the body surface, their general arrange ment and their configuration when grouped to gether. All these considerations help to eluci date the condition present.
In the etiology of skin diseases many fac tors are operative. For convenience of descrip tion these may be classed as internal causes and external causes. Among internal causes, hered ity may be mentioned first. While not many cutaneous diseases are inherited, the predisposi tion to them may undoubtedly be passed on to the child. This predisposition probably is due to some form of tissue vulnerability to influences which otherwise might not suffice to produce disease. Disorders of internal organs are fre quently effective. Their exact relation to the skin disorder may not be entirely clear; but the joint association of internal and cutaneous dis ease in many instances is too regular and fre quent to be a mere coincidence. Thus, gusts°, intestinal derangements may produce erythema, eczema or urticaria; whether these are due to the intestinal disorder or both due to a more primary emotional disturbance is still an open problem; kidney disease may cause an ec zema or pruritus; diabetes is not infrequently accompanied with boils, carbuncles, gangrene, dermatitis, urticaria or pruritus. Syphilis is attended with many forms of eruption; gout is frequently associated with eczema or psoriasis, and rheumatism with erythema and purpura. Asthma, eczema and urticaria are often found together. Lastly, emotional derangements may produce an array of functional disturbances in the skin and through reflex action on the vaso motor nerves may be the determining factor in the development of cutaneous lesions. The sex ual system unquestionably exerts an influence on skin diseases. The prevalence of acne in the young, following puberty, is well known, and various cutaneous derangements are associated with physiological crises and pelvic disorders in women. Food may 'produce skin. eruptions.
Urticaria-is not uncommon after ingestion of shell-fish, cheese or. strawberries and-the list of siiisperikaing articles could be greatly entreaded.
Eczema, acne and inflammatory conditions are greatly influenced by quantity and kind of food taken. Alcohol in inflammatory lesions is es pecially harmful Any of the many types of skin eruptions may develop following the use of certain drugs, the list of which is very extensive. Among those in most common use which may disturb the near tissues and hence the skin, are quinine, belladonna, morphine, arsenic, potassium bro mide and iodide.
Climate may be considered an external fac tor. Warmth and moisture found in tropical and subtropical countries are especially favorable to the growth of certain parasites in the skin. Cold and moisture tend to induce eczematous conditions. Certain diseases are distinctly prey alent in certain countries, but the fact is not always due to climatic influence alone. The sea sons differ also in their effect. Winter aggra vates pruritus, eczema and psoriasis; summer improves them. Light, heat and cold are capable of producing inflammatory conditions. On the other hand, light is distinctly ameliora tive in certain diseases, as psoriasis. Clothing when improper in amount, harsh of quality, poorly fitting, or uncleanly, can give rise to in flammation of the skin. Irritants of various sorts, whether mechanical, chemical or medici nal, can likewise awaken inflammation. Scratch ing and other traumatism are frequent causes of hyperaemia and dermatitis. Parasites, both vegetable and animal, are the most important of all external causes. A very large number of cutaneous diseases are traceable to them. Among the more common diseases produced by vegetable organisms are boils, carbuncles, vari ous pus infections and the different forms of ringworm ; by animal parasites, scabies and dermatitis from pediculi.
The number of cutaneous disorders under classification is about 170, but this does not include all tropical diseases. Of this seem ingly large number, many are rare, others are seen but seldom, while a few are very common. Dermatologists have not agreed upon a uniform classification of skin diseases; their differences, however, largely concern minor distinctions. The following general classes are usually given as a basis for further subdivision: (1) hyper arnias • (2) inflammations; (3) hemorrhages; (4) hypertrophies; (5) atrophies; (6) new growths; (7) neuroses; (8) diseases of the appendages; (9) parasitic affections. By some authorities diseases of the appendages are con sidered among the other classes, as inflamma tions, hypertrophies, etc. The difference in the classification, however, is not essential, being rather one of convenience.
Bibliography.— For further discussion of the subject the following authorities, amorg others, may be consulted: Hartzel, 'Diseases of the (•hiladelphia 1917) ; Ormsby, 'Dis eases of the Skin) (ib. 1915); Pusey, 'Prin ciples and Practice of (New York 1917) ; Shamberg, 'Diseases of, the Skin and the Eruptive Fevers) (Philadelphia 1915) ; Stelwagen, 'Diseases of the .Skin) (ib. 1916) • Sutton, 'Diseases of the {Saint. Loth.; 1417). . .
M.S..
As:ristent Professor in Dermatology, _Rusk Medical College, ClrieVo.