A section on diseases of the skin presents to the writer certain difficulties, not on account of the want of material, but rather from its redundancy. The reader may be inclined to observe, speaking from his own experience, that a very limited literature should be sufficient to deal with the affections which attack the exterior of the animal body. The contrary is in reality the case. Dermatology is a very wide subject, and during the past century a large number of most distinguished medical authorities on the Continent, especially in Germany and France, and also in England, have devoted almost exclusive attention to disorders of the skin. Among the writers in Germany the names of Ferdinand Hebra and Virchow, and in England Willan, Bateman, Erasmus Wilson, Todd Thompson, M'Call Anderson, Tilbury Fox, Malcolm Morris, may be mentioned among a host of other distinguished men. Willan's system of classification formed the basis of the other different systems which have from time to time attracted the attention of the scientist, but even some of our modern writers still hold that the system of Willan and Bateman is for practical purposes preferable to what is called the natural and the pathological systems of classification.
The first attempt to classify diseases of the skin was made by Hieronymus Mercurialis in 1572, by whom skin affections were divided according to their locality, as those of the head and those of other parts. This simple arrangement was added to by Daniel Turner, in 1743, and by Alibert in 1806, who subdivided the diseases. Scientific classification is said to have begun with Plenck, Vienna, 1776, who took as his basis the objective features of the diseases, grouping Affections of the Skin under fourteen heads: (1) Macules, (2) Pustules, (3) Vesicles, (4) Bullae, (5) Papules, (6) Crusts, (7) Scales, (8) Callosities, (9) Excrescences, (10) Ulcers, (11) Wounds, (12) Cutaneous insects, (13) Diseases of the nails, (14) Diseases of the hair.
This classification to some extent was modified by Willan, who used the terms (1) Papules, (2) Scales, (3) Exanthemata, (4) Bullae, (5) Pustules, (6) Vesicles, (7) Tubercles, (8) Macules; and Willan's pupil Bateman added Dermal excrescences.
Erasmus Wilson adopted an anatomical system of classification, grouping the skin affections according to the structures in which they arose, making four divisions: (l) Diseases of the derma, (2) Diseases of the sudoriparous glands, (3) Diseases of the sebiparous glands, (4) Diseases of the hair and hair follicles.
Hebra in 1845 adopted a pathological system, dividing skin diseases into twelve classes: (1) Hyperaemias, (2) Anaemias, (3) Anomalies of secretion of glands, (4) Exudations, (5) Haemorrhages, (6) Hypertrophies, (7) Atrophies, (8) Neoplasms, (9) Pseudoplasms, (10) Ulcerations, (11) Neuroses, (12) Diseases caused by parasites.
Dr. Tilbury Fox, whose work on skin diseases is constantly referred to by dermatologists, proposes a system of classification which he considers will be found the best for all practical purposes, in the following ten groups: - (1) Eruptions of the acute specific diseases, such as small-pox, etc.
(2) Local inflammations, including erythema, roseola, urticaria (nettle-rash) and certain medicinal rashes; catarrhal inflammations, as in eczema; papular inflammations, for example, lichen and prurigo; bullous inflammations, including herpes, &c; suppurative inflammations, including pustular eruptions; squamous inflammations, including pityriasis, rubra, and psoriasis.
(3) Diathetic disorders, including strumous and leprous diseases of the skin.
(4) Hypertrophic and Atrophic diseases, as warts, corns; and ichthyosis, affecting the epithelium; also keloid, fibroma, scleroderma, affecting the connective tissue of the skin; and among atrophies, senile decay and atrophy.
(5) New formations - cancer, lupus, and rodent ulcer. (6) Haemorrhages, for example, purpura. (7) Neuroses, as hyperesthesia, anaesthesia, and pruritis. (8) Pigmentary alterations. (9) Parasitic diseases, including animal or dermatozoic itch, and phthiriasis or lousiness, effects of fleas, bugs, gnats, etc, and vegetable or dermatophysis, as in different forms of ringworm. (10) Diseases of the glands and appendages, sweat glands and sebiparous glands, diseases of the hairs and their follicles, and diseases of nails.
This method of classification appears to be most applicable to the skin diseases of the horse.