BONES OF THE HAND. 



505 



HAIR. See TEGUMENTARY SYSTEM. 



HAND, BONES OF THE, (Human Ana- 

 tomy.) Tlic hand (YMf ( MMMj Vr. In main; 

 Grrm. illc llniiil,) is the inferior segment of 

 the upper extremity. Its presence is charac- 

 trn-.dc of man and the Quadrumana. 



Although formed on the same general type, 

 tin 1 hand will be found to exhibit many points 

 of difference from the foot characters strongly 

 indicative of the diversity of use for which it 

 is designed. In examining the skeleton of the 

 hand, we observe subdivisions analogous to 

 those which exist in the foot the carpus cor- 

 responding to the tarsus, the metacarpus to the 

 metatarsus, and the phalanges of the fingers in 

 every way analogous to those of the toes. 

 Independently of the lightness and mobility 

 which are such prominent features in the me- 

 chanism of the hand, when contrasted with 

 that of the foot, the divergence of the first or 

 radial finger (the thumb) from the line of 

 direction of the other four, is peculiarly cha- 

 racteristic of the hand. Whilst the four fingers, 

 properly so called, are parallel to the middle 

 line of the hand, the thumb, when extended, 

 forms with itan angle of rather more than 45. To 

 this position of the thumb is due in the greatest 

 part the facility of opposing it to one of the 

 fingers, a movement so necessary in the pre- 

 hension of minute objects.* 



The general form of the hand is oval, the 

 obtuse extremity corresponding to the tips of 

 the fingers, the unequal lengths of which oc- 

 casion the curvature in this situation. On its 

 ]x>sterior surface or dot-sum, the hand is convex ; 

 on its anterior surface or palm, it is concave : 

 both these surfaces correspond to, and in the 

 recent state are supported by, the bones of the 

 carpus and metacarpus. 



I. Carpus (Germ, die Handwurzel). The 

 carpus bears a much less proportion in size to 

 the whole hand than the tarsus does to the foot; 

 it forms scarcely more than one-fourth of the 

 hand. Its outline is oval, the long axis being 

 transverse : if examined in a hand to which 

 the ligaments are attached, the carpus will be 

 found to form the posterior and osseous portion 

 of an osseo-ligamentous ring, which gives pas- 

 MUC to the tendons of the fingers. It is con- 

 sequently hollowed from side to side, and is 

 bounded on each side by a bony ridge, which 

 gives attachment to the ligament (annular 

 ligament) which forms the anterior part of the 

 ring ; on the radial side the ridge is formed by 

 a process of the os trapezium and of the sca- 

 phoid ; on the ulnar, where there is a more 

 prominent ridge, by a process of the unciform 

 bone, and by the os pisifonne. 



Seven bones, arranged in two rows, form 

 the carpus. The superior row consists of the 

 o. nnviciilnrc, os lunarc, and os cuncif urine, 

 to which last is articulated a bone, constantly 

 reckoned as a carpal bone, but which, I con- 

 ceive, may be more correctly regarded as a 

 sesamoid bone, the os pisft'on/ie. The second 



* See the prefatory observations to ihc article 

 FOOT. 



or inferior row is formed by the us trapezium, 

 os trapczuidi'i, os inugnai/i, and us unci/uniie. 



1. Os navicularc (os seapliuidfuin ; Fr. A 

 s( -apluiiJe ; Germ, ilus Kulntbein). The na- 

 vicular or scaphoid is the largest of the upper 

 row, and likewise the most external. Its su- 

 perior surface is convex, oval, with long axis 

 transverse, articular, and is adapted to the 

 outer part of the carpal articular extremity of 

 the radius. The hollowed surface, to which it 

 owes its name (boat-Like), is directed down- 

 wards and inwards ; this is likewise articular and 

 receives the head of the os magnum : con- 

 tinuous with and to the inner side of this 

 hollow surface, there is a plane one of a semi- 

 lunar form, with which the os lunarc is articu- 

 lated. The scaphoid bone articulates with the 

 trapezium and trapezoides, by a convex surface 

 directed downwards and outwards. Externally 

 this bone terminates in a pointed extremity 

 which receives the external lateral ligament of 

 the wrist-joint and the annular ligament (tuber- 

 culum ossisnaviculuris, s.eminentiii curpiradialis 

 superior). The anterior and posterior surfaces 

 of the bone are rough, and give attachment to 

 the anteriorand posterior radio-carpal ligaments. 



2. Os lunare, (oi semilunare v. lunatum ; 

 Fr. le sfinilunaire ; Germ, das Mondbein), 

 situated between the scaphoid and the cunei- 

 form bones, it presents four articular surfaces ; 

 an upper one, convex and somewhat triangular 

 in its outline, articulated with the radius ; an 

 inferior one, very much hollowed from before 

 backwards (to the crescentic form of which the 

 bone owes its name), articulated with the os 

 magnum; an external surface, plane and 

 square, adapted to the cuneiform bone ; and, 

 lastly, an internal surface, by which it articu- 

 lates with the scaphoid. 



3. Os cuneiforme (os trujiietrum s. pura- 

 midale; Fr. le pyramidale; Germ.dasdreiseitige 

 Beia). This bone terminates the superior 

 carpal row on the ulnar side ; its upper surface 

 is partly smooth, encrusted with cartilage in 

 the recent state, where it is in contact with the 

 triangular ligament of the wrist-joint, and 

 partly rough where it gives attachment to liga- 

 ments. Externally it articulates with the cunei- 

 form bone, and inferiorly with the unciform 

 by a large and concave suaface. The inner 

 half of its anterior surface articulates with the 

 pisiform bone, and the radial half of the same 

 surface is rough for ligamentous insertion. 



The three bones just described, constituting 

 the superior row of the carpus when united, 

 present on their superior aspect a convex arti- 

 cular surface which forms the carpal portion 

 of the radio-carpal joint, the scaphoid and 

 lunar being articulated with the radius, while 

 the cuneiform glides upon the triangular carti- 

 lage of the wrist. 



4. Os pisijorme (from pisum, a pea; Fr. 

 le pisi/brme; Germ, das Erbsenbein). This 

 little bone projects at the anterior part of the 

 ulnar extremity of the superior carpal row ; 

 it forms what some anatomists designate 

 fwiiifHtin carpi utnuris *u/n run; lH'iii'_' p.ui nl 

 the bony ridge already referred to on the ulnar 

 side of the carpus. The prominence produced 



