ARTICULATIONS OF THE THORACIC LIMB — THE CARPAL JOINTS 205 



Articulations of the Thoracic Limb 



SHOULDER joint 



Ox. — The articular angle is about 100°. 



Pig and Dog. — The joint capsule communicates freely with the bicipital bursa. 

 There is a rudimentary marginal cartilage around the rim of the glenoid cavity. 

 In the dog there is usually a strong band extending from the acromion to the outer 

 part of the capsule; another band (Ligamentum coraco-acromiale) often stretches 

 between the scapular tuberosity and the acromion. 



ELBOW JOINT 



Ox. — No important differences exist. The upper part of the interosseous 

 radio-ulnar ligament is commonly ossified in the adult. 



Pig. — There are no important differences. The radius and ulna are so firmly 

 united by the interosseous ligament as to prevent any apprecial)le movement 

 between them. 



Dog. — The joint capsule is reinforced in front by an oblique ligament which 

 arises on the front of the external condyle of the humerus above the joint surface, 

 and joins the terminal part of the biceps and brachialis below. The external 

 lateral ligament is thick and divides into two parts; the anterior part is attached 

 to the radius and blends with the annular ligament; the posterior part widens 

 below, forming a sort of cap, and is attached to the ulna. The internal lateral 

 ligament also divides into two branches; the anterior branch ends on the inner 

 surface of the neck of the radius; the posterior enters the interosseous space and 

 is attached to both bones. An elastic band (Ligamentum olecrani) extends from 

 the outer surface of the internal epicondyle to the anterior border of the ulna. 



There are two radio-ulnar joints. The proximal radio-ulnar joint is included 

 in the capsule of the elbow, l)ut is provided with an annular ligament which extends 

 from the lower part of the external ligament across the front of the proximal end 

 of the radius to the ulna, blending with the biceps and brachialis tendons. The 

 distal joint is formed by a concave facet on the radius and a convex one on the 

 radius, and is surrounded by a tight capsule. The interosseous membrane unites 

 the shafts of the two bones. The movements consist of limited rotation of the 

 radius (ca. 20°), carrying the paw with it. The ordinary position is termed prona- 

 tion; outward rotation is supination.^ 



THE CARPAL JOINTS 



These have the same general arrangement as in the horse. Numerous minor 

 differences naturally exist, but must be excluded from this brief account, which 

 contains only important special features. 



The lateral movements are freer, especially in the dog, but flexion is not so 

 complete: the anatomical explanation of these facts lies in the nature of the articu- 

 lar surfaces and certain ligamentous differences. The lateral ligaments are much 

 weaker, the long external one being especially small in the ox. Two oblique, 

 somewhat elastic, bands cross the front of the radio-carpal and intercarpal joints. 

 The proximal one is attached to the distal end of the radius and passes downward 

 and outward to the ulnar carpal bone; the other one connects the radial and fourth 

 carpal bones in a similar fashion. 



In the ox the short lateral ligaments are well defined, a ligament connects 



^ These movements are best seen in man, in whom the back of the hand may be turned for- 

 ward (pronation) or backward (supination). 



