FISH-SKIN DISEASE (ICHTHYOSIS).—A disease characterised by dry ness of the skin of the entire body. The natural fat of the skin is absent ; it is rough and lustreless, and appears as if covered with dust. The upper most layer of the skin is variously fissured, especially on extensor surfaces, so that smaller or larger, round or polygonal, scale-like plates develop. The scales are either thin, white, and glistening, or thick. and of a greenish grey colour. In the centre they adhere to the base, whereas they are free at the edges, and they constantly drop from the skin. The armpit, elbow-joint, knee-joint, and the inguinal fold are exempt from the disease. Owing to the fissures of the upper layer of the skin, the malady is annoying and unsightly, but it is never dangerous. The treatment consists of baths, soap ablu tions, and embrocations of fat. Ichthyosis is probably a hereditary affection.
FISTULA.—.An abnormal, more or less narrow passage which either leads from a cavity of the body, or from the interior of an organ, to the surface of the body ; or establishes a connection between two organs, as, for instance, between the bladder and the vagina. Complete fistulas are to be distinguished from blind ones in that the latter have but one opening.
Fistulas are mostly due to deep-seated, chronic, purulent inflammations, which finally discharge through the skin (bone and breast fistulas). They may result from injuries ; for instance, from penetrating foreign bodies such as bullets or splinters which were not removed in time ; or from the injury due to long-lasting pressure of the infant's head in difficult deliveries. This last-named cause may give rise to a fistula between the bladder and the vagina. Disturbances of the development of the foetus in the womb frequently give rise to fistulas by causing parts to remain open which should have been united (throat and navel fistulas).
Fistulas are named according to their location, or according to the fluid discharged from them. Thus, in many old tuberculous bone-diseases, tuber culous fistulas develop. These lead down to dead and dying bone. Openings from the intestines result in fmcal fistulas. With regard to rectal fistulas, which are very common, see RECTUM, DISEASES or. The treatment of the affection, which rarely heals spontaneously, often encounters great diffi culties ; surgical interference is normally required.