410 



THE ANATOMY OF THE HORSE 



THE ELBOW JOINT 



C)i: THE HUMERO-UADio-LLNAU AIM u I i.vTiuN. — This joint 18 formed betwccu 

 till' lower extremity «>f the humerus above, and the junction of the radius 

 and ulna below. It is a complete hini^'e, and has no power of pronation or 

 supination lus in man. eonseijuently there is no necessity for the peculiar 

 additional joint between the radius and ulna, observ- 

 al)le in man and partially in the dog and cat ; but tho 

 two bones are firmly ossified together in the adult, 

 as already described at page 379. 



These bones are connected together l)y three liga- 

 ments, two lateral (an internal and an external), a 

 capsular ligament, and a sj-novial capsule. 



Tlie intermd lateral lli/ament arises from a fosi-a 

 I n\ the side of the internal condyle of the humerus ; 

 it takes a vertical course, expanding as it descends : 

 imd is inserted partly on the roughened inner border 

 of the articular cavity of the radius. Its middle fibres, 

 v.'hich are tho longest, take the same course as the 

 formei-, assuming while passing over the radius the 

 shape of a cord, which is inserted into the inner and 

 fore part of the radius about three inches below the 

 former insertion. 



TJie external lateral liyament is shorter but stronger 

 than the internal. It arises from the superior fossa 

 and ridge surrounding it, on the outer surface of the 

 external condyle of the humerus, and is inserted into 

 the tuberosity on the upper and external part of the 

 radius. Its superficial fibres take a vertical coui-se, 

 whilst its internal fibres take an oblique direction, 

 from top to bottom and from back to front. 



The capsular lif/ament is attached by its superior 

 border to the surfaces surrounding the cond^des of the 

 humerus ; by its infenor border, to the circumference 

 of the superior part of the radius ; and by its posterior 

 Ixinlcr to the circumference of the articular surface of the ulna. 



The sifnuvial membrane is short anteriorly, very extended, and spread out 

 p>steriorly ; where it forms three sacs, which tend to facilitate flexion of 

 the joint. 



TiiK M0VEMENT.S of the elbow joint are confined to flexion and extension, 

 it being a pure hinge, but these actions do not take place exactly in the 

 same plane. For instance, if the knee is bent and the foot brought up to 

 the ell)ow, the frog will not correspond with that projection, but will be 

 almost entirely outside it, while the knees will also be wider apart when 

 both are llexed and raised towards the bosom, than when the horse is stand- 

 ing. This arrangement is brought about by the oblique direction of the 

 l>ulley-like articular surfaces on the humerus, ulna, and radius, and appeal's 

 to \yo designcfl to prevent the foot from hitting the opposite leg as it passes 

 it in trotting. When the obliquity is insufficient, either cutting of the 



Fm. 40.— rosTERion View 

 Of l-EfT Elbow Joint. 



A. rnfi'riorthird of the Im- 



iiienis. 

 D. n. Extornnl nnd iiitomnl 



condylps. 

 C. Olecranon process of 



ulna. 

 P. I(.idius. 



1. External lateral liga- 



ment. 



2. Internal lateral lifpi- 



ment. 



3. 3. Filiro - rartilnKinons 



sulxst-ineo unitiri;; thr 

 ulna to the Kuliii-i. 



