DEFORMITIES, variations in the form of the body as a whole, or in one or more of its parts, constituting a depar ture from the normal conditions of struc ture, and usually implying a correspond ing divergence from natural and healthy functions. They may be divided into three groups, with reference to their ori gin—the hereditary, the congenital, and the acquired. The first group is charac terized by a marked tendency to recur rence in the line of direct descent from generation to generation, as in those cases where the presence of extra fingers or toes has become characteristic of many members of one family.
The chief varieties of malformation, coming under the heading of congenital deformities, are the following: (1) As regards the number of parts. In the Si ren, two lower extremities are fused into one mass, but dissection shows that all the constituent bones of the limb may be present, though much distorted, in the combined structure. In the Cyclops, the eyes are similarly fused into one irregu lar structure occupying the center of the face. (2) As regards the size of parts.
This may involve the whole body, as in dwarfs, of whom ther'e have been some remarkable peripatetic specimens: the Corsican fairy was only 2 feet inches high. Deformities the opposite of this
exist, such as giants, or instances of premature or excessive local growth. O'Byrne, the Irish giant, measured 8 feet 4 inches when he died at the age of 22. Such individuals are generally subject to premature decay. (3) As regards the shape and continuity of parts. Distor tion may occur from partial paralysis or irregular muscular action at an early stage of development, giving rise to club-foot, club-hand, etc.; or natural fissures or apertures which should close in the course of development may remain open, as in harelip, cleft palate, and spina bifida.
Acquired deformities arise in various ways as the result of injury or disease at any period after birth. Another group of these affections, known as "trade" de formities, are directly traceable to the special work done by the person suffering from them. See DARWINIAN THEORY.