ELBOW (ARTICULATION OF TII rivxcer, cubitus ; Fr. coude ; Germ. elbogen ; elbow or humero-cubital articulation is an angular ginglynius formed by the inferior articular extremity of the os humeri and the superior articular extremities of the radius and ulna, the surfaces of which are, in the recent state, covered with a cartilaginous incrustation, and kept in apposition by an ex tensive synovial capsule, an anterior, a poste rior, and two strong lateral ligaments.
The muscles which cover this articulation are, the bmchimus anticus, the inferier tendon of the triceps, and some of the muscles of the fore-arm anteriorly, the triceps and aoconaeus posteriorly, and the superinr attachments of several of the muscles of the fore-arm laterally.
Bones.—The lower part of the humerus is flattened before and behind, and curved a little forwards : an obtuse longitudinal ridge, on a line corresponding to the lesser tuberosity at its superior extremity, divides it into two slo ping surfaces anteriorly, while posteriorly it presents a broad, flat, triangular surface : a sharp ridge on each side terminates below in a rough tuberosity, called a condyle ; the exter nal condyle is the smaller of the two, and when the arm hangs loosely by the side, it is directed outwards and forwards : the internal condyle is much larger, more prominent, and directed inwards and backwards: a line let fall per pendicularly from the most prominent part of the greater tuberosity above would fall upon the external condyle ; the internal condyle bears a similar relation to the centre of the superior articular head of the humerus. The inferior articular surface extends transversely, below and between the condyles, and presents a series of eminences and depressions; begin ning at the external side, a small spheroidal eminence, the eminentia capitata or lesser head, situated on the front of the external condyle, directed forwards and received into the circular cavity on the head of the radius, internal to this is a small grooved depression which lodges the internal part of the border of that cavity : the remainder of this surface forms a sort of pulley, to which the greater sigmoid cavity of the ulna corresponds; this, which is called the trochlea, presents a large depression placed be tween two raised ridges : the depressed portion of the trochlea winds round the lower extre mity of the humerus in an oblique direction from before backwards and a little outwards, being broader behind than in front ; its external border forms a semicircular ridge, smooth in front and sharp behind, the anterior part of which corresponds to the division between the radius and ulna; its internal margin also forms a semicircular ridge, sharper and more promi nent than the external, and which projects half an inch below the internal condyle, having be tween it and this latter process a sinuosity in which the ulnar nerve lies ; it is the prominence of this ridge which determines the obliquity in the direction of the humerus, observable when its inferior articular extremity is placed on a horizontal surface.
Behind and above the trochlea a large trian gular depression (fossa posterior) receives the olecranon in extension of the fore-arm ; a simi lar depression of smaller size (fbssa anterior) receives the coronoid process in flexion ; these two fosse' are separated by a plate of bone, often so thin as to be diaphanous, and some times they communicate by an aperture, the longest diameter of which is transverse, as in the quadrumana, carnivore, glires, and pachy dermata; Aleckel is of opinion that the exist ence of this aperture in the human subject is more frequent in the Negro and Papuas than in the Caucasian race ;$ however it did not exist in any one of three Negroes and four Mulattoes which I dissected, while I possess two specimens of it, and have seen several others which occurred in Europeans : a second small fossa frequently exists above in front of the eminentia capitata, into which the head of the radius is received in complete flexion.