ANATOMY AND PHYSIOLOGY OF THE HORSE'S FOOT. 181 
which lead directly into its interior, and that there they are 
largest, some of the most capacious being situated immediately 
in front of the “ scaly ” or “ patilobe eminence.” In laminitis 
we know that the anterior portion of the foot suffers most 
severely, and that the subsequent pathological changes, result- 
ing in deformity of the wall of the hoof and the sole, are 
principally confined to this portion. I have constantly re- 
marked that these changes rarely extend further back than 
the termination of these foramina and the commencement of 
the patilobe eminences. The reason for this may become 
apparent hereafter. 
So numerous are these conduits around the lower thin 
edge of the bone, that it not unfrequently looks notched and 
broken, and in other places appears like a veritable rabbit- 
warren in miniature, for smooth-surfaced holes are burrowed 
out everywhere, and generally in an oblique direction, or run 
along the steep surface for some distance. One of these 
spaces passes along in a horizontal manner on each side, 
separating the patilobe eminence and retrossal process below 
from the basilar process and lateral depression above, and is 
so marked a feature in this aspect of the bone as to have 
received the name of preplant ar fissure (fig. 4 ,j). So notice- 
able and peculiar is this series of external perforations, that 
an anatomist who happened to be unacquainted with the 
organization of the horse's foot would at once pronounce it 
to be an organ endowed with the highest degree of vascu- 
larity, from a mere casual examination of the outside of this 
artful circulatory contrivance. Wonderful, however, as may 
appear the arrangement of channels and perforations on the 
exterior of the bone, it is even more so if we follow these up 
to their sources in the interior. By clipping and rasping 
away the enveloping osseous texture,* we perceive that all 
the infinitely minute and comparatively large tunnels, which 
appear to ramify everywhere in the most perplexing manner, 
converge towards the centre, to form what is called a sinus, 
or cavity of a semilunar shape (fig. 5, h), lying in a horizontal 
direction, and, like the smaller spaces, having cylindrical 
walls which are composed of the densest and strongest bone. 
This beautiful and complete system of viaducts, which affords 
ingress and egress to countless vessels, and serves to a great 
* I need scarcely say that the readiest way to expose these internal 
vascular channels is to soften the bone by maceration in diluted hydrochloric 
acid, when, owing to the earthy salts having been removed, the organic 
matter is easily cut and the canals displayed. When it is desired to keep 
the vessels intact, then, of course, this procedure is inadmissible, and the 
chisel must be resorted to. 
