102 THE SKELETON OF THE HORSE 
remarked that the bone is twisted slightly; when placed volar surface down on the table, it touches 
the latter by three points only, the proximal tuberosities and the medial condyle. 
THE SECOND PHALANX 
The second phalanx (Phalanx secunda)! is situated between the first and 
third phalanges, its direction corresponding to that of the first phalanx. It is 
flattened from before backward, and its width is greater than its height. It may 
be described as possessing four surfaces. 
The proximal surface presents two glenoid cavities separated by a low ridge, 
and articulates with the first phalanx. 
The middle of the dorsal border is ele- 
--= Proximal vated and roughened in front for the 
sesamotds attachment of the common extensor 
tendon. The volar border is thick and 
overhanging; in the fresh state its mid- 
dle part is covered with cartilage, over 
which the deep flexor tendon passes. 
On either side there is an eminence, to 
_-First which the collateral ligament and the 
phalans: superficial flexor tendon are attached. 
The distal surface is trochlear, 
and articulates with the third phalanx 
and distal sesamoid bone. It resem- 
bles somewhat the trochlea of the first 
phalanx, but is more extensive and en- 
croaches more on the dorsal and volar 
surfaces. 
The dorsal surface is convex from 
side to side and smooth in its middle; 
on each side of its distal part is a rough 
Tuberosity -- 
Ridges for 
allachment. == 
of middle 
distal sesa- 
moid ligament 
Imprint for 
tendon of 
superficial 
flexor 
Condyle --~ 
Transverse 
prominence ~~ 
_ Second 
Condyle _ phalanx 
Proximal Distal depression, surmounted by a tuber- 
border -___ sesamoid osity, to both of which ligaments are 
Peron imine sttached, 
ibn ~ | The volar surface is smooth and 
Angle - fay — é flattened. The borders which separate 
es PEN. ay aes the dorsal and volar surfaces are con- 
Volar be cave from above downward, rounded 
from before backward. 
Development.—The second pha- 
lanx ossifies like the first, but the proxi- 
, mal end unites with the shaft two or 
Fr ae three months earlier. 
ie hird 
phalanx 
foramen - 
Semilu- --54 
nar crest 
Flexor 
5 - 
surface 
THE THIRD PHALANX 
Fic. 80.—Dieirat Bones or Fore Limp or Horse; VOLAR 
Aspner. The third phalanx (Phalanx ter- 
tia)? is entirely inclosed by the hoof, 
to which it conforms in a general way. It presents for examination three sur- 
faces, three borders, and two angles. 
The articular surface (Facies articularis) faces upward and backward, and is 
chiefly adapted to the distal surface of the second phalanx, but a narrow, flattened 
area along the volar border articulates with the distal sesamoid. The proximal or 
coronary border bears a central eminence, the extensor process (Processus exten- 
1'This bone is also called the small pastern bone or os coronx. 
2 This bone is also called the os pedis or coffin bone. 
