THE SKELETON 41 



by the lips of the coracoid and pro-coracoid, and serves for the 

 attachment of MM. pectoralis and supra-coracoideus. At about the 

 same level on the other side of the bone is the crista dorsalis humeri 

 (cr.d.h.). This is a smaller hooked process and does not extend on 

 to the head of the humerus. M. subscapularis is inserted on it. 

 Immediately distal to the point from which these crests arise the 

 humerus is approximately circular in cross-section, but it very soon 

 expands in an axial plane, i.e. at right angles to the expansion of the 

 head. On the pre-axial border of the distal end is the epicondylus 

 lateralis humeri (co.l.h.), a fairly pronounced ridge, partly osseous 

 and partly cartilaginous, which gives rise to the MM. extensor 

 antebrachii et carpi radialis, and extensor digitorum communis and, 

 in part, to the M. extensor antebrachii et carpi ulnaris. On the 

 postaxial border is a similar ridge, the epicondylus medialis humeri 

 (co.m.h.), from which arise the flexor muscles antagonistic to those 

 above mentioned. The radial condyle (co.r.) (Eminentia capitata^ 

 Gaupp) is large, and forms about two-thirds of a complete sphere, 

 standing out prominently from the surrounding structures towards 

 the ventral, or flexor, surface of the arm. The ulnar condyle (co.u.) 

 is much smaller, and is approximately semi-elliptical in shape, while 

 between the two condyles is a shallow trochlear groove (fs.tr.). Both 

 condyles and groove are entirely cartilaginous. The fossa cubitalis 

 centralis (fs.cu.v.)(Gaupp), into which the end of the radius fits when 

 the arm is flexed, is very deep and well marked, but the olecranon 

 fossa (fs.ol.) is shallow and indefinite. 



(b) The Fore-Arm (figs. 25-7 and 39-41). The radius and ulna 

 are completely separate, and of approximately equal length and 

 average size. The proximal end of the radius^ or pre-axial element 

 (figs. 39—41), is more or less circular in section, and the bone tapers 

 fairly evenly to the middle of the shaft where the smallest diameter is 

 reached; there being only a very small crest on the ventro-mesial 

 surface. The epiphysial cartilage of the proximal end is slight and 

 saucer-shaped; its concavity is shallow. The distal end of the radius 

 expands in an axial direction so that, when seen from the extensor 

 or flexor surfaces, it is roughly triangular in shape. The cross-section 

 of this end is approximately rectangular, and the cartilaginous 

 epiphysis is more extensive on the pre-axial side than on the post- 

 axial. It articulates with the pars intermedia of the fused ulnare 

 + intermedium and also with the radiale. 



The ulna (figs. 25-7), in contrast to the radius, is larger at its 

 proximal end and smaller distally. The club-shaped proximal end 

 is trapezoid in section, the longest side being mesial. The epiphysis 



