THE ANTERIOR LIMBS. 



73 



Angles. The anterior or cervical angle is the thinnest of the three. The 

 posterior or dorsal anjle is thick and tuberous, The inferior or humeral 

 angle is the most voluminous, and is separated from the remainder of the 

 bone by a slight constriction, which constitutes the neck of the scapula. It 

 exhibits : 1, The glenoid cavity, an oval diarthrodial surface, excavated to a 

 slight extent to receive the head of the humerus, notched on the inner side, 

 and bearing on the external margin of the ridge which surrounds it a small 

 tubercle of insertion; 2, The coracoid process, situated in front, and at a 

 certain distance from the glenoid cavity. This is a large eminence 

 in which may be distinguished two parts : the base, a thick rugged process ; 

 and the summit, a kind of beak curved inwards. 



Structure and development. Like all the wide bones, the scapula is 

 formed of two compact lamellae separated by spongy tissue. The latter is 

 yery scanty towards the centres of the supra and infraspinous fossae, where it 

 is often altogether wanting ; it is most abundant in Fio . 41 



the angles. The scapula is developed from two centres 

 of ossification, one of which forms the coracoid pro- 



cess. 



ABM. 



This region has only one bone, the humerus. 



Humerus. 



The humerus is a long single bone, situated between 

 the scapula and the bone of the fore-arm, in an oblique 

 direction downwards and backwards. Like all the long 

 bones, it offers for study a body and two extremities. 



Body, The body of the humerus looks as if it 

 had been twisted on itself from within to without in 

 its superior extremity, and from without to within at 

 the opposite end. It is irregularly prismatic, and is 

 divided into four faces, The anterior face, wider 

 above than below, has in its middle and inferior por- 

 tions some muscular imprints. The posterior, smooth 

 and rounded from one side to the other, becomes 

 insensibly confounded with the neighbouring faces. 

 The external is excavated by a wide furrow, which 

 entirely occupies it, and turns round the bone ob- 

 liquely from above to below and behind to before , 

 it is to the presence of this channel that the humerus 

 owes its apparent twist, and it is in consequence 

 designated the furrow of torsion of the body of the 

 humerus. 



This furrow is separated from the anterior face 

 by a salient border, the anterior crest of the furrow 

 of torsion, which ends inferiorly above the coronoid 

 fossa, and superiorly, towards the upper third of the 

 bone, by the imprint, or deltoid tuberosity. This is a 

 joughened, very prominent eminence, flattened before 

 and behind, and inclining towards the furrow of 

 torsion ; by its superior extremity it gives origin to 

 a curved line which is carried backwards to join the 

 base of the articular head. Near the inferior extremity, backwards and 



ANTERO-EXTERNAL VIEW 

 OP EIGHT HUMERDS. 



1, Trocblear or bicipital 

 ridges; 2, External or 

 deltoid tuberosity ; 3, 

 Head or articular sur- 

 face ; 4, External tuber- 

 cle; 5, Shaft or body with 

 its twisted furrow ; 6, 7, 

 Articular or trochlear 

 condyles ; 8, Ulnar fossa 

 with a sulcus , 9, Fossa 

 for the insertion of the 

 external lateral liga- 

 ment. 



