ANATOMY AND PHYSIOLOGY OF THE HORSE’S FOOT. 667 
that margins it as far as its inflexions within the sole ; its 
upper border stands out sharp and prominently from the 
groove, while its lower edge subsides almost insensibly into 
the coronary zone. 
In texture this cushion differs essentially from that of 
the plantar surface, being composed of a very close and firm 
fibrous tissue, identical with that of the derm ; multitudes of 
arteries from various large trunks send their ramifications 
into its structure and over its surface, to compose a most 
intricate network, which is so close and interwoven as to form 
a complete vascular tissue on its face. The whole of its 
convex surface is lodged, or rather rests, within a correspond- 
ing concavity on the upper and inner face of the wall of the 
hoof. When this latter has been removed in the fresh state 
by an extreme degree of heat, the coronary cushion often 
resembles in colour the bright red of flesh, from the great 
quantity of blood it contains ; and when it does not do so, it 
is owing to no lack of blood-vessels, but to the absence of 
blood in them, or the presence of black pigment granules 
diffused in its outer layer, as in the dark coloured epiderm 
immediately adjacent. Though most commonly of a bright 
red or scarlet hue, its tint somewhat depends upon that of 
the integument in connection with the hoof, as if this be 
brown or black it is then of a darker shade. 
The “ coronary ” or “ white zone ” (fig. 12, d ) appears, on 
a superficial inspection, to be merely a continuation of the 
cushion, whose lower margin it terminates. On a careful 
examination, however, we discover that, though constituting 
a portion of this elastic and secretory body, it yet presents 
some points which distinguish it more or less, and which must 
be referred to here. It begins as a very narrow band in front, 
between the cushion and the podophyllse beneath, being in an 
ordinary sized foot less than a quarter of an inch in width. 
As it approaches the heels it gradually expands, and at the 
inflexures has attained somewhat considerable dimensions. 
It passes in the same direction as the cushion, and extends 
beyond it on the inner surface of the wings of the pedal bone. 
It has a slightly more prominent convexity than the cushion ; 
its colour, more particularly where it abuts on the laminae, is 
lighter than that of the cushion, though in black legged 
horses it is sometimes faintly flecked with dark streaks or 
spots. 
The coronary cushion and its zone derive their most re- 
markable peculiarity from the presence of the vast numbers 
of papillae or villosities which crowd their surface everywhere, 
giving it, as the foot floats in water, a filamentous appear- 
