83' THE BONES OF THE UPPER LIMB. 



The cranial bones increase in size principally at their margins ; and when a suture is 

 prematurely obliterated the growth of the skull in the direction at right angles to the line of 

 suture may be supposed to be checked, and increased growth in other directions may take 

 place to supply the defect. Thus, the condition known as scaplioeeplwly is found associated 

 with absence of the sagittal suture, where, the transverse growth being prevented, a great 

 increase takes place in the vertical, and especially the longitudinal directions, giving the vault 

 of the skull a boat-like form. Similarly, acroeeplialy is related to obliteration of the coronal 

 suture, the compensatory growth taking place mainly upwards. Oblique deformity, or 

 plagiocephaly, also is met with in connection with premature fusion of one half of the coronal 

 or lambdoid suture ; but indrpenc 1 entry of this a precisely similar deformity may be induced by 

 rickets, wry -neck, cr external pressure. (See Virchow, " Gesammelte Abhandlungen," 1856; 

 Lucae, " Zur Architectur des Menschenschadels," 1857; W. Turner in Xat. Hist. Rev., 1864 ; 

 J. Barnard Davis, "On Synostotic Crania," 1865; Topinard, op. cit.) Another series of 

 irregular forms of skull is that produced by pressure artificially applied in early life, and is 

 best exemplified from among those American tribes who compress the heads of their children 

 by means of an apparatus of boards and bandages : it is also illustrated in a slighter degree by 

 individual instances in which undue pressure has been employed unintentionally. (Gosse, 

 " Essai sur les Deformations artificielles du Crane," 1855 ; V. Lenhossek, " Die kiinstlichen 

 Schadelverbildungen," &c., 1881.) Posthumous distortions likewise occur in long-buried 

 skulls, subjected to the combined influence of pressure and moisture. (Wilson, " Prehistoric 

 Annals of Scotland.") 



IV. THE BOWES OF THE UPPER LIMB. 



The upper limb consists of the shoulder, the arm, Irachium, the forearm, anti* 

 brachium, and the hand, manus. The bones of the shoulder are the clavicle and 

 scapula, which together form the pectoral arch or shoulder-girdle ; in the arm is the 

 humerus ; in the forearm are the radius and ulna ; and in the hand three groups of 

 bones, viz., the carpus, metacarpus, and phalanges. 



THE CLAVICLE. 



The clavicle or collar-bone extends out wards and backwards, from the summit of 

 the sternum to the acromion process of the scapula, and connects the upper limb 

 with the trunk. It is curved like an italic/: the internal curve has its convexity 



- On) CONOID TUB.- 



Fig. 85. RIGHT CLAVICLE, FROM ABOVE. (Drawn by T. W. P. Lawrence.) 



directed forwards, and extends over two-thirds of the length of the bone ; the 

 outer curve is concave forwards, corresponding to the hollow between the chest and 

 shoulder. 



The clavicle is broad towards its scapular end, being compressed from above 

 downwards, but in the extent of its inner curve it is more or less prismatic or 

 cylindrical. In its description, four surfaces may be distinguished, together with the 

 two extremities. 



The superior surface is broadest in its outer part ; it is principally subcutaneous and 

 smooth, but near the inner extremity presents a slight roughness, marking the clavi- 



