THE THIRD PHALANX 103 
sorius), to which the common extensor tendon is attached. On either side is a de- 
pression for the attachment of the collateral ligament. 
The dorsal or wall surface (Facies dorsalis) slopes downward and forward. 
The angle of inclination on the ground plane is about 45 to 50 degrees in front. 
Cartilage a 
Extensor process 
Depression for collateral ligament 
Dorsal surface 
b Dorsal Angle Distal border 
groove 
Fie. 81.—Tuirp PHartanx oF Horse; Larerar View. 
a, b, Anterior and posterior extremities of cartilage. 
Laterally the height diminishes, and the slope becomes steeper, especially on the 
medial side. From side to side the curvature is almost semicircular. The surface 
is rough and porous, resembling pumice stone somewhat. It is perforated by nu- 
merous foramina of various sizes; a series of larger ones is situated on or near the 
distal border. On either side the dorsal groove (Sulcus dorsalis)? passes forward 
from the angle and ends at one of the 
largerforamina. In the fresh state this 
surface is covered by the corium of the 
wall of the hoof. The distal border is 
thin, sharp, and irregularly notched; 
there is commonly a wider notch in 
front. 
The volar surface (Facies volaris) 
is arched, and divided into two unequal 
parts by a curved rough line, the semi- 
lunar crest (Crista semilunaris). The 
larger area in front of the crest is cres- 
cent-shaped, concave, and compara- 
tively smooth; it corresponds to the 
sole of the hoof, and may be termed 
the sole surface. The part behind the 
crest is much smaller, and is semilunar; 
it is related to the deep flexor tendon, 
and is hence called the flexor surface Fic. 82.—Secrion oF Torrp PHALANX OF Horse. 
(Facies lexoria). It presents a central ,.. on 5 ‘Mt apmoxnetaly panel wth volar ur 
prominent rough area, on either side of — amina indicated by arrows. 
which is the volar foramen (Foramen 
volare), to which the volar groove (Sulcus volaris) conducts from the angle.’ 
The foramina lead into the semilunar canal (Canalis semilunaris) within the 
bone, from which small canals lead to some of the foramina of the dorsal sur- 
1 Formerly termed the pyramidal process. ? Formerly termed the preplantar groove. 
’ Formerly termed the plantar groove and foramen. 
