THE ANTE BIOS LIMBS. 75 



remarked : outwardly, an excavation for ligamentous insertion ; inwardly, 

 a small tuberosity intended for the same purpose.' 



Structure and development.— ^The humerus, like all the long bones, is 

 only spongy at its extremities. It is developed from six points of ossi- 

 fication ; one of which alone forms the body, one the head and the small 

 trochanter, another the large trochanter, a fourth the inferior articular 

 surface, a fifth the epicondyle, and the last for the epitrochlea. The latter is 

 sometimes absent. 



FOEB-AEM. 



This region has for its base two bones, the radius and cubitus (or ulna) 

 united into a single piece at an early period in most of the domesticated 

 animals. 



1. Radius. 



This is a long bone, placed in a vertical direction between the 

 humerus and the first row of carpal bones, and divided into a lody and 

 two extremities. 



Body. — Slightly arched and depressed from before to behind, thre body 

 presents for study two faces and two borders. The anterior face is convex 

 and perfectly smooth. The posterior, a little concave from one extremity to 

 the^other, offers : 1, Near the external border, a triangular surface, covered 

 with^asperities, elongated vertically, very narrow, commencing near the 

 upper fourth of the bone and terminating in a fine point towards the lower 

 fourth : this surface is brought into contact with the anterior face of the 

 ulna by an interosseous ligament, which is completely ossified before the 

 animal reaches adult age^ 2, Above, there is a wide, transverse, but shallow 

 groove, which aids in forming the radio-ulnar arch and shows, near the point 

 where it touches the preceding surface, the nutrient foramen of the bone ; 

 ■ 3, Near the internal border, and towards the inferior third, there is a ver- 

 tically elongated and slightly salient eminence of insertion. The two 

 borders, external and internal, are thick and rounded; they establish an 

 insensible transition between the faces. 



Extremities. — The superior is larger than the inferior. It has : 1, An 

 articular surface elongated from one side to the other, concave from before 

 to behind, wider within than without, and moulded to the articular surface 

 of the inferior extremity of the humerus ; there is also seen, outwardly, a 

 double gorge which receives the two lips of the external trochlea ; in the 

 middle, an anteroposterior ridge which is received into the internal trochlea ; 

 within, an oval cavity corresponding to the internal border of the former ; 

 2, The external tuberosity, placed at the extremity of the great diameter of 

 the articular surface; it is prominent and well detached ; 3, The internal or 

 bicipital tuberosity, a large, very rugged, and depressed process, situated 

 -within and in front of the glenoid cavity ; 4, A little lower, and on the same 

 side, there is a strong muscular and ligamentous imprint, separated from the 

 preceding tuberosity by a transverse groove intended for the passage of a 

 tendinous branch ; 5, The eoronoid process,^ a small conical eminence, at the 

 summit of which terminates, anteriorly, the median ridge of the articular 



' The articular surfaces which, in veterinary anatomy, have received the names of 

 trochlea and condyle, not being the same as in human anatomy, there results an annoying 

 inversion of the situation of the epitroehlean and epicondyloid eminences, so named. It 

 has therefore been our endeavour to remedy the. improper employment of these 

 denominations, which has been a cause of error in comparative anatomy. 



' In Man this belongs to the ulna. 



