ANATOMY AND PHYSIOLOGY OF THE HORSe’s FOOT. 427 
growth or ergot of the fetlock against the perforatus tendon. 
The other branch ascends forwards, and, reaching as high as 
the small metacarpal or metatarsal bone, fixes itself on the 
little button or knob by which the extremity of that bone ter- 
minates. At the other or lower extremity these ligamentous 
bands pass obliquely forward, and are inserted into the wings 
of the foot bone. This arrangement of the fibrous covering 
of the plantar cushion is very curious and interesting, forming 
as it does a complementary ligamentous apparatus of much 
moment in connection with the elasticity of the foot. 
At the sides, the plantar cushion is wider than the perforans 
tendon, and is limited by the inner faces of the lateral car- 
tilages, to which it is closely attached by bands of fibres that 
pass through it from side to side, by prolongations from the 
cartilages themselves, which dip deeply into the structure of 
the cushion, and become incorporated with it, and, finally, by 
a real continuity of texture towards its lower border. 
Its convex apex, inclining forwards, is firmly fixed into the 
sole of the os pedis, in advance of the tendon, with whose 
fibres it mixes ; while the base or heels, directed backwards, 
is of great thickness, and divided inferiorly by a deep de- 
pression into two bulbous masses corresponding to the horny 
frog at this part, having a membranous covering between it 
and the skin of the pastern above and the secreting mem- 
brane of the horny frog below, and which might be termed 
the “ inferior tunic” of the plantar cushion. This tunic is 
fixed on each side to the posterior border of the lateral 
cartilage, and joins, in front and above, the superior tunic, to 
become attached to the sheath of the flexor tendons. 
On each side the cushion effects the most intimate relations, 
by means of fibrous attachments, with the lateral cartilages 
and wings of the pedal bone, and in this way becomes allied 
in function with the coronary cushion ; while above and in 
front it is so related to the deep flexor tendon, even as high 
as the pastern joint, and to the movements of that tendon on 
the navicular bone, as to render it a powerful agent in 
ensuring the accomplishment of those resilient functions 
pertaining more particularly to the foot. 
The lower face of the plantar cushion is that which has 
been commonly termed the fleshy or fatty frog, and offers the 
same contour as the horny frog, of which, in fact, it is but a 
reduplication. The heels or “ cartilaginous bulbs” of the 
cushion are the prominent and most posterior portions, sepa- 
rated from each other on this face by a deep angular space, 
called the “ median lacuna of the plantar cushion from 
them proceed the branches which, uniting towards the 
