THE HORSE, 



45 



OS BRACHII (arm bone). 



Q. Describe the location of the os 

 brachii. — A. It is located beneath the tho- 

 rax, in the inferior region of the humerus. 



Q. How does this bone differ from those 

 of the human subject ? — A. By being con- 

 solidated into a single bone. 



Q. How is it divided ? — A. Into radial 

 and ulnar portions. 



Q. Describe the radial. — A. It consists 

 of a body, superior and inferior extremi- 

 ties. The body is lengthy, compared with 

 other bones of the fore extremity ; posteri- 

 orly it is excavated and roughened ; ante- 

 riorly it projects with a smooth, cylindrical 

 surface. 



Q. Describe the superior extremity. — 

 A. The superior extremity presents an in- 

 terrupted articulatory surface, having a 

 central eminence, with two cavities, which 

 correspond to the articulations of the os 

 humerii. 



Q. Describe the inferior extremity. — 

 A. It appears to consist of three articulatory 

 surfaces, which correspond with those of the 

 bones of the carpus. 



Q. Describe the ulnar portion of the os 

 brachii. — A. It presents a tapering trian- 

 gular projection, firmly connected with the 

 radius ; at its junction with the same, it 

 presents a semilunar concavity ; this, with 

 the articulatory surface of the radius, forms 

 the humero-brachial articulation. 



Q. Name the projection of the ulnar, 

 commonly termed point of the elbow. — A. 

 Olecranon. 



Q. What muscle is inserted into the ole- 

 cranon ? — A. The triceps extensor brachii. 



Q. What is the state of this bone in 

 early colthood ? — A. It is composed of two 

 pieces named radius and ulnar, which after- 

 wards become consolidated. 



Q. With what bones does the inferior 

 portion of the os brachii articulate ? — A. 

 With the scaphoid, lunar, and cuneiform 

 bones. 



BONES OF THE KNEE (cARPUS). 



The bones of the knee correspond to the 

 wrist, or carpus, of man. 



Q. How are these bones arranged ? — A. 

 They are ranged in tv^o rows, or ders ; one 

 of the number, trapezium, is located in the 

 posterior part of the carpus. 



Q. Name the bones of the first row ? — 

 A. Scaphoid, lunar, cuneiforme, trapezium. 



Q. Name the bones crossing the second 

 row ? — A. Pisiform, trapezoid, magnum, 

 unciform. 



Q. What is the general form and situa- 

 tion of each of the bones of the first row? 

 — A. The OS scaphoides is semi-ovoid in 

 form, its superior surface is sigmoid and 

 smooth, the inferior surface is somewhat 

 oval, and rests upon the trapezoides and 

 magnum of the second row. Its internal 

 surface comes in contact with the os lunare. 

 The OS lunare is the second bone of the first 

 row ; it articulates superiorly with the 

 brachii ; inferiorly, with the ossa magnum 

 and unciforme ; its superior surface is trian- 

 gular ; inferior, oblong ; on one side, inter- 

 nally, it articulates with the scaphoid, on 

 the other with the cuneiforme. The cunei- 

 forme is known as the external, yet smallest 

 bone of the knee. Its superior surface is 

 concave ; inferior, smooth ; its internal sur- 

 face articulates with the os lunare, and pos- 

 teriorly it unites with the trapezium. 



Q. What is the general form and situa- 

 tion of each of the bones of the second 

 row ? — A. The os trapezoides is situated 

 on the inner side of the knee, resting on the 

 inner splent bone, and articulating with the 

 OS magnum ; its form is that of an irregular, 

 curvated, flattened cone ; its superior surface 

 is convex, and its inferior flat. The os 

 magnum is the middle bone of the second 

 row, and is known as the largest bone of 

 the knee. Its superior surface presents two 

 articulatory surfaces, one sigmoid and ob- 

 long for the OS lunare, and the other ovoid 

 and flat, to correspond with the surface of 

 OS scaphoides; its interior surface is flat, 

 and articulates with large metacarpal bone. 

 The OS unciform is situated on the outer 

 side of the second row, and in form resem- 

 bles a blunt hook; its superior surface is 

 convex; its inferior irregular, articulating 

 with the outer splent and cannon. The os 



