378 THE ANATOMY OF THE HORSE 



divided into three portions by projecting lines — First, a middle groove, which 

 terminates in front in the coronoid fossa and behind in the olecranon fossa, 

 each being for the reception of the corresponding processes of the ulna and 

 radius, thereby checking the motion of the joint. Second, the external 



7 



Flu. 25.— Internal View of left HuMERrs. 



A. Body or shaft. 5. Internal depression to which the internal lateral 



1. Tlie head. ligament is attached. 



2. Tubercles on the head. 6. Back jiart of inner condyle. 



3. Internal tubercle. 7. Internal condyle. 



4. Scabrous tubercle. 



groove, which is comparatively slightly marked ; and third, the smooth 

 surface lining the internal condyle. All of these fit accurately into the 

 articular surface of the ulna and radius, to be presently described, allowing 

 of nothing but a hinge-like motion. Of the condyles, the inner is larger and 

 more projecting than the outer. 



In the young foal the two extremities arc distinct epiphyses, united to 

 the shaft b}- cartilage only. 



THE BONES OF THE FORE-ARM (OS BRACHII) 



In the hujian subject, and in the dog and cat among our domestic 

 animals, the bones of the fore-arm are distinct, and may readily be separated 

 from each other as the ulna and radius. In the early periods also of the 

 life of the horse the same condition obtains, but when he is matured, these 

 bones are indissolubly united by ossification. The line of junction can 

 always be traced, and there is an opening left which is called the radio- 

 cuhital arcade, and gives passage to an artery and vein. It will be therefore 

 understood that the term os hrachii means the bone composed of the united 

 ulna and radius, and that in alluding to each of these divisions we only 

 speak of tlicm, in analogy with human anatomy, as separate bones. By 



