Though the human hand seems to be a fairly uniform structure, it really shows a differentiation as wide as that of the features of the face. It is a well-known fact that the character of an individual can in a measure be read in his features, and a similar connection with haracter can be found in the form of the hand. The hand, however has a closer connection with actual occupation. Whereas the influence of vocation on the traits (apart from a natural disposition for a certain craft that may lead to its adoption) is due mainly to a particular turn of mind connected with and produced by that vocation, the influence exerted on the shape of the hand is mainly of a physical nature. The continual repetition of the same kind of manual work results in a permanent alteration of the skin and muscles of the hand, as well as a transformation of the bones (atrophy or thickening of certain parts), displacement of the joints, etc., for in repeating a given manipulation over and over again, the palm and the balls of the thumb and little finger are called upon continually to perform the same action, leading to a permanent strain on and wear and tear of given parts of the hand. The most obvious alterations due to occupation are observed in the case of heavy manual laborers, who have, coarse and clumsy hands with short, thick, and callous fingers, the balls of the thumb and the little finger bing especially developed, and the skin being horny and covered with fissures. While these properties generally are especially striking in the right hand, it is sometimes even more interesting to study the left hand of individuals, as for instance in the case of a smith, who by continually using this hand to seize the heavy tongs, develops very marked balls and projecting broadened finger tips (Fig. 1). The thumb of his left hand in fact is used continually in pressing on the tongs, and so becomes especially strong. The right hand shows the marks f its continual use in handling the heavy hammer, while the fingers assume a shortened, clumsy shape. Similar facts, though to a less degree, are stated in the case of locksmiths. A very striking sample of a deformed hand is represented in Fig. 2, which shows the hand of a shoe- * With six photographs by Carl F. Schroeder, Magdeburg. maker. This is characterized by the strikingly broad and flat thumb, while the fingers are likewise broadened and flattened at the top. This deformation is due to the continual pressure exerted in cutting the leather for the heels and soles, which operation calls for considerable strength, the fingers being set firmly against the surface of the hard leather, while the knife is kept in the fist. A continual pressure is furthermore brought to bear on the finger tips in working the heavy material, while the callous balls become strikingly thickened. The shape of the right-hand forefinger is also characteristic of the profession, tha surface turned toward the thumb being flattened considerably, so as to give the finger a tapering form. This is due to the continual use of that part of the forefinger in seizing, and fitting shoenails and tacks, resulting in a rsorption of both the bone and flesh. The left thumb being used mainly to keep the object in position in nailing the leather, is not quite as broad and flat as the right-hand thumb. The striking deflection of the right thumb is well visible in Fig. 2. Another type of hand, viz., that of a typesetter, is represented in Fig. 3. This is of a , slender, regular shape, showing that the work done is not heavy. The actions connected with his profession are mainly performed by means of the thumb and forefinger of the right hand, the tips being used nearly exclusively in picking the type from the cases and inserting it in a narrow "stick" held in the left hand. This continual seizing by means of the thumb and forefinger tips is bound to result in an atrophy of the bones and tissues, which is especially marked in the surfaces turned toward each other. Both the thumb and the forefinger of the right hand accordingly show a tapering form in their upper parts, while the remaining fingers retain their normal broad tips. The left-hand thumb, owing to the permanent pressure exerted by the type box, is flattened and broadened at the tip. The hand of a tailor, with smooth palm, likewise shows a striking difference from that characteristic of a man who does heavy work. The forefinger of the left hand of a tailor is especially characteristic, as the lateral surface turned toward the thumb shows a striking wear and tear at the tip, giving the finger a pointed shape. This phenomenon is due to the needle continually sliding over this part of the finger, which, as it were, serves as support to the needle, the thumb and forefinger holding the material. After examining the hands of representatives of certain handicrafts, it will be interesting to study that of an artist. The hands represented in Figs. 5 and 6 are those of a pianist, which show some especially characteristic features. In fact, all of the ten fingers are remarkably flat at the tips on the side coming in contact with the keys of the instrument, as a consequence of the variable pressure permanently exerted on the latter. Furthermore, the fingers are strikingly long, as their members, in swiftly touching the keys of high and low notes, are loosened continually. On the other hand, the thumb and little finger, which spread out in opposite directions, are elongated to a considerable degree, and the other fingers, as well as the remainder of the hand, are likewise affected by this process. While a study of the different types of hand is bound to appeal to the lover of psychology and sociology, it has been found recently to be a valuable aid to the criminal police in ascertaining the profession of a suspect. Like the various methods of determining the physical characteristics of an individual, which have been suggested in the course of recent years, an investigation of these factors may in fact give useful hints as to the identity of an individual.
This article was originally published with the title "The Influence of Profession on the Shape of the Hand" in Scientific American 97, 26, 478 (December 1907)