102 



EXTREMITY. 



sixth year ; from the eighth to the ninth year 

 tlit! ossilic elements of tlie lit'utl of the liume- 

 rus become united and the head is com- 

 pleted. 



The inferior extremity of the humerus, accord- 

 ing to Cruveilhier, begins to ossify later than the 

 superior. The first point of ossification noticed 

 in it is for the external condyle : this appears at 

 the age of two years and a half; at seven years 

 a second point of ossification commences for the 

 epitrochlea; at twelve a third point appears for 

 the internal edge of the trochlea; and at sixteen 

 years a fourth point for the epicondyle. These 

 four points of ossification, Cruveilhier states, are 

 united in the following order: first, in the 

 second year, the two points of the trochlea are 

 united; and, secondly, at sixteen years the 

 trochlea, epicondyle, and the condyle form a 

 a single piece.* The union of the extremities 

 with the shaft of the bone takes place from the 

 eighteenth to the twentieth year ; and all ob- 

 servers agree in stating that the union of the 

 inferior extremity with the shaft always pre- 

 cedes that of the superior extremity, although 

 the ossification of the latter is prior. 



forearm. The bones of the forearm are 

 the ulna and radius, of which the former con- 

 stitutes the second essential element in the 

 elbow-joint, the radius being chiefly an acces- 

 sory bone to provide for the wider range of 

 motion of the hand. The ulna therefore is the 

 principal lever of the forearm, and the motions 

 of flexion and extension of that segment of 

 the limb upon the arm depend upon it ; at its 

 superior extremity it forms a very firm hinge- 

 joint with the trochlea of the humerus, but in- 

 feriorly its connexion with the carpus at the 

 wrist-joint is very slight, and it forms by no 

 means an essential element of that joint On 

 the other hand, the radius at its inferior ex- 

 tremity forms a very important part of the 

 wrist-joint, but at its superior its connection 

 with the elbow-joint is due to its necessary 

 articulation with the outer side of the ulna. 



Ulna (xt/j3iTo, cubitus; Fr. os du coude ; 

 Germ, das EUenbogcnbein.-f) This bone is 

 situated on the inner side of the forearm. It is 

 the longest and the largest bone of that region, 

 and in the vertical position of the limb it is 

 directed downwards and a little outwards, the 

 obliquity being occasioned by the greater pro- 

 jection downwards of the inner lip of the 

 trochlea of the humerus, as already alluded to 

 in describing that bone. 



The upper or humeral extremity of the ulna 

 is at once distinguished by its great size from 

 the inferior extremity. It consists of two pro- 

 cesses joined to each other at a right angle, and 

 so that that angle opens forwards. One of 

 these processes is vertical, and is continued in 



* C'ruveilhier, Anat. Descr. lorn. i. p. 231. 



t The term facile was a( plied to this bone as well 

 as to (lie radius by some of the ancient anatomists, 

 in imitation of the Arabians, who used the word 

 zen/1, sc\ an instrument analogous to our tinder-box, 

 which consisted of two sticks, similar in appear- 

 ance and proportions to the bones of the forearm. 

 Focile majus was the ulna, focile minus the radius. 

 IfluiiH nbach, Beschreibung Uer Knochcn, p, 395. 



the direction of the long axis of the bone, and 

 is little else than a continuation of the shaft ; 

 this is the olecruium : the other is horizontal, 

 anterior to the olecranon, as it were placed 

 upon the superior extremity of the bone, so 

 as to project considerably beyond the plane 

 of its anterior surface : this is the coronoid 

 process. 



The olecranon, (wXem, cubitus, xgao, caput,) 

 also called processus ancontcus, may be said to 

 begin from the angle of junction of the coro- 

 noid process with it ; there the bone appears 

 slightly constricted, for above that point it ex- 

 pands. We notice five surfaces upon it. The 

 superior surface is horizontal ; it presents pos- 

 teriorly a muscular impression affording inser- 

 tion to the triceps extensor, and anteriorly it 

 ends in a remarkable beak, which, in the state 

 of complete extension, is received into the ole- 

 cranon cavity of the humerus. The posterior 

 surface is rough with a very obviously trian- 

 gular outline; this surface gives insertion 

 to the triceps muscle. The internal surface 

 is also rough, and covered by the fibrous ex- 

 pansion from the tendon of the triceps, and 

 at its anterior margin affords insertion to the 

 superior fibres of the internal lateral ligament. 

 The external surface is smooth, and also is 

 covered by the fibrous expansion from the ten- 

 don of the triceps. The anterior surface is 

 articular ; it presents the appearance of having 

 been covered by articular cartilage ; it is divided 

 by a rounded vertical ridge into two unequal 

 portions, of which the internal is larger than 

 the external. This surface is limited below by 

 a transverse depression, non-articular, in which 

 some fatty matter is deposited in the recent 

 state. The surface is convex from side to side 

 in the centre, and each of its lateral portions is 

 concave; the whole surface is concave from 

 above downwards. In the extended state of 

 the forearm this articular surface of the olecra- 

 non is applied to the posterior part of the 

 trochlea of the humerus ; it forms the posterior 

 part of the great sigmoid cavity of the ulna. 



The coronoid process is wedge-shaped, at- 

 tached by its base to the anterior surface of the 

 ulna, the sharper edge projecting forwards and 

 free. This edge is convex, and sometimes 

 forms a point ; it is received into the coronoid 

 cavity of the humerus. On the external mir- 

 jace of the coronoid process is an oval articular 

 facet, concave from behind forwards, whose 

 long axis is horizontal ; this is the lesser sigmoid 

 cavity, and is articulated with the inner side of 

 the head of the radius ; the internal surface is 

 rough, and lias a projecting lip, which affords 

 attachment to the anterior fibres of the internal 

 lateral ligament. The anterior surface is in- 

 clined from above downwards and from before 

 backwards, so that its aspect is downwards and 

 forwards ; it is slightly hollowed transversely, 

 and is rough, the roughness being continued 

 down for a little way in front of the bone, thus 

 forming a rough surface triangular in form, the 

 base corresponding to the anterior edge of the 

 coronoid process ; this surface affords insertion 

 to the brachiteus anticus muscle. The superior 

 surface forms the anterior portion of the great 



