368 THE HORSE. 
small metacarpal bone. (See 5, Fig. 12.) It is united on the outer side 
with the external lateral ligament, and internally with the common poste- 
rior ligament. To its posterior border are attached the outer fibres of the 
sheath of the flexor tendons. 
The synovial capsules proper to these articulations line all the above 
ligaments and articular surfaces, being reflected from one to the other, 
and forming also pouch-like prolongations upwards between the bones of 
each row, as far as the interosseous hgaments, and 
downwards in a similar manner. Neither of the 
ascending pouches is continuous with the radio- 
carpal capsule, but the external of the two lower 
communicates with that of the carpo-metacarpal 
joint. This fact is sometimes important in punc- 
tured wounds of the knee joint. 
2. THE RADIO-CARPAL ARTICULATION, formed by 
the union of the lower end of the radius with the 
upper surfaces of the scaphoid, lunar, cuneiform, 
and pisiform bones, is a true hinge, but sometwhat 
limited in the amount of its motion. The lower 
end of the cannon-bone can describe fully ninety 
degrees of a circle around the knee joint as a 
centre; but the full extent of this motion is divided 
between the three several articulations to which 
IT have alluded, the radio-carpal taking considerably 
the largest share. Zhe lower end of the radius 
presents an irregular articular surface, longer from 
side to side than from before backwards, and a 
non-articular pit or fossa hollowed out to receive a 
Pio. IL—_Awrerror View or Projection of the lunar bone during the flexion of 
tuk Lert Kner Joinr. the joint. On each side of these are the lateral 
A. Inferior third of the ra- Processes. The upper surfaces of the carpal bones are 
eet moulded exactly to fit the inferior extremity of the 
c. Lunar bone. radius, and a loose synovial capsule passes from one 
Y iBeephon Done: to the other, extending downwards between the 
G. The great bone. three innermost carpal bones as far as their inter- 
i pee ny ea Pete et quetas OSSEOUS ligaments, and sometimes also to the capsule 
ao Seno ent between the pisiform and cuneiform bones. _ 
2. External lateral ligament. § Zhe ligaments proper to this articulation, in ad- 
8. 8. Internal lateral liga- dition to those common to the whole knee joint, are 
4, 4, Ligaments existing be- three. Of these one forms a large rounded cord, 
p  Meeleaiteea ee °f attached to the radius above, and to the cuneiform 
5. 5. Carpo-metacarpal liga- hone below, taking an oblique direction downwards 
ment. : A c 
and inwards beneath the common posterior liga- 
ment. The second, much smaller in size, is extended between the 
external lateral process of the radius and the pisiform bone, being par- 
tially covered by the common external lateral ligament, but allowing a 
small triangular space to intervene, through which the synovial capsule is 
sometimes protruded in diseased conditions of this joint. The third, still 
more thin and weak in its fibres, is situated beneath the second, and arising 
from the radius is inserted in the lunar bone, and into the interosseous 
ligament which unites the pisiform and scaphoid bones. (See 3, Fig. 13). 
(3) THE CARPO-METACARPAL ARTICULATION is formed above by the 
three inferior carpal bones, and below by the heads of the three metacarpal 
bones, together constituting a limited hinge joint. These surfaces above 
