254 THE SKELETON. 



to flex or extend the forearm moves the fragment and not the joint. (2) The presence of small 

 portions of muscular tissue between the broken ends. (3) Want of support to the elbow, so 

 that the weight of the arm tends to drag the lower fragment away from the upper. An import- 

 ant distinction to make in fractures of the lower end of the humerus is between those that 

 involve the joint and those which do not ; the former always serious, as they may lead to 

 impairment of the utility of the limb. They include the T-shaped fracture and oblique frac- 

 tures which involve the articular surface. The fractures which do not involve the joint are the 

 transverse above the condyles and detachment of one or other condyle. 



Under the head of separation of the epiphysis two separate injuries have been described. 

 One where the whole of the four ossific centres which form the lower extremity of the bone are 

 separated from the shaft ; and secondly, where the articular portion is alone separated, the two 

 condyles remaining attached to the shaft of the bone. The epiphysial line between the shaft 

 and lower end runs across the bone just above the tips of the condyles, a point to be borne in 

 mind in performing the operation or excision. 



Tumors originating from the humerus are of frequent occurrence. A not uncommon place 

 for a chondroma to grow from is the shaft of the bone somewhere in the neighborhood of the 

 insertion of the deltoid. Sarcomata frequently grow from this bone. 



THE FOEEAEM. 



The Forearm is that portion of the upper extremity which is situated between 

 the elbow and the wrist. It is composed of two bones, the ulna and radius. 



The Ulna. 



The Ulna (Figs. 200, 201), so called from its forming the elbow (wAswj), is a 

 long bone, prismatic in form, placed at the inner side of the forearm, parallel with 

 the radius. It is the larger and longer of the two bones. Its upper extremity, of 

 great thickness and strength, forms a large part of the articulation of the elbow- 

 joint ; it diminishes in size from above downward, its lower extremity being very 

 small, and excluded from the wrist-joint by the interposition of an interarticular 

 nbro-cartilage. It is divisible into a shaft and two extremities. 



The Upper Extremity, the strongest part of the bone, presents for examination 

 two large, curved processes, the Olecranon process and the Coronoid process ; and 

 two concave, articular cavities, the greater and lesser sigmoid cavities. 



The Olecranon Process (a^ewy, elbow ; xpaviov, head) is a large, thick, curved 

 eminence situated at the upper and back part of the ulna. It is curved forward 

 at the summit so as to present a prominent tip, its base being contracted where 

 it joins the shaft. This is the narrowest part of the upper end of the ulna, 

 and, consequently, the most usual seat of fracture. The posterior surface of the 

 olecranon, directed backward, is triangular, smooth, subcutaneous, and covered 

 by a bursa. Its upper surface, directed upward, is of a quadrilateral form, marked 

 behind by a rough impression for the attachment of the Triceps muscle ; and in 

 front, near the margin, by a slight transverse groove for the attachment of part of 

 the posterior ligament of the elbow-joint. Its anterior surface is smooth, concave, 

 covered with cartilage in the recent state, and forms the upper and back part of 

 the great sigmoid cavity. The lateral borders present a continuation of the same 

 groove that was seen on the margin of the superior surface ; they serve for the 

 attachment of ligaments ; viz. the back part of the internal lateral ligament 

 internally, the posterior ligament externally. To the inner border is also attached 

 a part of the Flexor carpi ulnaris, while to the outer border is attached the 

 Anconeus. 



The Coronoid Process (xopwvr], anything hooked like a crow's beak) is a rough, 

 triangular eminence of bone which projects horizontally forward from the upper 

 and front part of the ulna, forming the lower part of the great sigmoid cavity. 

 Its base is continuous with the shaft, and of considerable strength ; so much so 

 that fracture of it is an accident of rare occurrence. Its apex is pointed, slightly 

 curved upward, and received into the coronoid depression of the humerus in 

 flexion of the forearm. Its upper surface is smooth, concave, and forms the 

 lower part of the greater sigmoid cavity. The under surface is concave, and 

 marked internally by a rough impression for the insertion of the Brachialis anticus. 

 At the junction of this surface with the shaft is a rough eminence, the tubercle of 



