THE FORE-ARM. 337 
IN THE YOUNG FoaL, the two extremities are distinct epiphyses, united 
to the shaft by cartilage only. 
Fig. 25.—INTERNAL VIEW orf Lerr HuMERUS. 
A. Body or shaft. 5. Internal depression to which the internal 
1. The head. lateral ligament is attached, 
2. Tubercles on the head. 6. Beck part of inner condyle. 
3. Internal tubercle. 7. Internal condyle. 
4. Scabrous tubercle. 
THE BONES OF THE FORE-ARM (OS BRACHII). 
IN THE HUMAN sUBJECT, and in the dog and cat among our domestie 
animals, the bones of the fore-arm are distinct, and may readily be sepa- 
rated 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 ma- 
tured, 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-cubital arcade, and gives passage to an artery and vein. It will 
be therefore understood that the term os brachti means the bone composed 
of the united ulna and radius, and that in alluding to each of these 
divisions we only speak of them, in analogy with human anatomy, as 
separate bones. By drawing a line from the back of the condyle of the 
humerus till it euts the posterior edge of the shaft of the os brachii about 
its middle, the line of demarcation may easily be arrived at. 
Tue Raprus forms the bulk of the os brachii, supporting the weight of 
the body upon its head, and conveying it to the carpus through its lower 
extremity. Its skaft is long, smooth, and convex anteriorly ; rough for 
the attachment of muscles, and concave posteriorly. The superior ex- 
tremity is expanded, and presents an articular surface divided into two 
fossee by a slight ridge, the inner of the two being broader and more 
circular. On each side of these pits is a slight projection, called the 
lateral process, to which the corresponding ligaments are attached. The 
inferior extremity, which is also expanded, is remarkable for the variously 
shaped pits slightly marked on its articular surface, each being intended 
to fit one of the carpal bones of which the knee is made up. There is a 
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