190 
subcutaneous and covered by a bursa. 
OSTEOLOGY. 
Its superior aspect, which forms with the 
posterior surface a nearly rectangular projection—the tip of the elbow—furnishes 
OLECRANON PROCESS 
GREAT SIGMOID 
CAVITY 
Anconeus 
Brachialis 
anticus 
SMALL SIGMOID 
CAVITY 
| _ TUBEROSITY 
~Supinator radii brevis 
~BICIPITAL HOLLOW 
Extensor ossis metacarpi 
pollicis 
POSTERIOR BORDER 
~ Extensor carpi ulnaris 
INTEROSSEOUS BORDER 
Extensor longus pollicis 
~Extensor indicis 
ARTICULAR SURFACE 
FOR RADIUS 
GROOVE FOR EXT. CARPI 
ULNARIS 
STYLOID PROCESS 
Fria. 134.—Tar RigHt ULNA AS VIEWED 
FROM THE OUTER SIDE. 
CORONOID PROCESS 
a surface for the insertion of the tendon of the 
triceps muscle, together with a smooth area which 
is overlain by the same tendon, but separated 
from it by a bursal sac. To the anterior crescentic 
‘border of this process are attached the fibres of the 
posterior part of the capsule and portion of the 
internal lateral hgament of the elbow joint. The 
anterior surface is articular, and enters into the 
formation of the great sigmoid cavity. ; 
The coronoid process (processus coronoideus) is 
a bracket-like process, which juts forwards from 
the fore and upper part of the shaft, and is fused 
with the olecranon process superiorly. By its 
upper surface it enters into the formation of the 
ereat sigmoid cavity, whilst its anterior aspect, 
which is separated from its upper side by a sharp 
irregular margin, slopes downwards and backwards 
to become confluent with the anterior surface of 
the shaft. Of triangular shape, this area, which 
is rough and tubercular, terminates inferiorly in 
an oval elevated tubercle (tuberositas ulnee), into 
which the tendon of the brachialis anticus muscle 
is inserted. Of the lateral margins of the coronoid 
process, the inner is usually the better defined. 
Above, where it joins the superior border, there 
is generally a salient tubercle, to which one of 
the heads of origin of the flexor sublimis digi- 
torum muscle is attached, whilst below this point 
the inner border furnishes origins for the pronator 
radii teres, and occasionally for the flexor longus 
pollicis muscles, from above downwards. The 
smooth inner surface of the coronoid process 
merges with the olecranon behind, and with the 
internal surface of the shaft below. 
The great sigmoid cavity (incisura semilunaris), 
for articulation with the trochlea of the humerus, 
is a semicircular notch, the upper part of which 
is formed by the anterior surface of the olecranon, 
whilst below it is completed by the upper surface 
of the coronoid process. Constricted towards its 
deepest part by the notching of its lateral borders, 
the articular surface is occasionally crossed by a 
narrow impression which serves to define the 
olecranon process above from the coronoid below. 
The articular area is divided into an inner 
portion, slightly concave transversely, and an 
outer part, transversely convex to a slight degree, 
by a longitudinal smooth ridge which extends 
from the most prominent part of the border of 
the olecranon above to the most outstanding point 
of the coronoid process below. The margins of 
the great sigmoid cavity are sharp and. well de- 
fined, and serve, with the exception of the area 
occupied by the small sigmoid cavity, for the 
attachment of the capsule of the elbow joint. 
The small sigmoid cavity, placed on the outer side of the coronoid process, is an 
oblong articular surface for the reception of the head of the radius. 
It encroaches 
