ANATOJVIV OF THE HORSE. 
427 
HUMERUS. 
Situation .—Between the scapula and the arm; placed in an 
oblique but contrary direction to the scapula, viz. downwards 
and backwards; whereby an angular space, of considerable 
extent, is left between the two bones. 
Form .—Cylindroid ; presenting the appeamnce of having been 
twisted round itself. 
Division .—Into a body and two extremities. 
Body. —Angular, with expanded flattened sides, superiorly; 
contracted and rounded, inferiorly. From its upper, fore, and 
outer part, projects the tuberosity; whose point is roughened by 
the insertion of the levator humeri. The outer side of the body is 
excavated and smooth; it is occupied by the humeralis extemus : 
the inner side is rather prominent and roughened, and exhibits a 
small scabrous eminence, which receives the tendons of the latis- 
simus dorsi and teres major ; also, lower down, we find the 
medullaiy foramen, pointing downwards. 
Superior extremity —Larger than the inferior, presents 
for consideration a head and four tubercles .—The head is the 
hemispherical smooth part projecting posteriorly: it is designed 
for articulation with the glenoid cavity of the scapula, which it 
much exceeds in extent of superficies, and thereby obtains moi*e 
freedom and variety of motion. Into the in’egular and indented 
groove by which the head is surrounded, is fixed the capsular 
ligament. Anteriorly, the head is surmounted by the tubercles : 
the three directly in front are anti-articular, and have between 
them two smooth grooves, which, as well as themselves, are 
covered by cartilage, and altogether serve as a pulley for the ten¬ 
don of the flexor brachii to play over. The outer articular 
tubercle is j oined by a protuberant ridge with the tuberosity. 
The fourth, or outer tubercle, serves to guard against dislocation. 
Inferior extremity —Displays a specimen of the diar- 
throdial or pulley-like articulation. It consists of two condyles, 
distinct from each other posteriorly, being there' separated by a 
deep ovoid fossa, into which is received the olecranon of the 
ulna; but united, inferiorly and anteriorly, into a broad semi- 
cylindrical articular surface, divided by a prominence encircling 
its middle into two depressed compartments, of which the inner 
has twice the breadth of the outer, and bounded by two lateral 
prominent edges: furthermore, the condyles, of which the inner 
is larger and more projecting behind as well as before,, meet at 
an angle above the fossa, and there vanish in union with the 
body. There are also two scabrous pits above the articular sur- 
