ANATOMY AND PHYSIOLOGY OF THE HORSE^S FOOT. 643 
wall. But the vexed question immediately arises,, Are the 
keraphyllae produced from the coronary cushion or from the 
podophyllse ? And if they are not from the latter, then what 
is the function of these ? 
Pathological observation might appear to favour the sup- 
position that these horn leaves are really secreted by the 
living ones around the pedal bone; whereas anatomy and 
physiology lend their evidence to prove that such is not the 
case, and that the horny laminae are an integral portion of 
the wall, are formed with it, and in a healthy foot do not owe 
their production to the vascular laminae. So contradictory 
did the observations acquired appear, and in so much 
obscurity did the question remain until recently, that recourse 
was had to direct experimentation to set the matter at rest. 
With this object it was first deemed necessary to ascertain 
the exclusive share taken in the keratogenous function by the 
coronary cushion when isolated from all the parts in its 
vicinity ; therefore a section of the wall was removed from 
below upwards, so as to lay completely bare the vascular 
laminae and the surface of the cushion for an equal width 
throughout, while a transverse incision separated these two 
parts, and the laminae were entirely excised from the pedal 
bone, leaving the exposed part of the cushion alone to form 
a new section. In a few days a layer of concrete horn was 
exuded from this surface to repair the breach, and below the 
process of granulation was going on to compensate for the 
loss of the podophyllous tissue. In about a month a horny 
tumour, to all external appearance the same as that formed 
in the first experiment, had been constituted at the origin of 
the hoof, immediately beneath the hair, but below this growth 
the breach remained as wide and complete as at the moment 
after the operation, owing to the vascular laminae having 
been destroyed. In three or four months, during which time 
care was assiduously taken to prevent the formation of a 
cicatrice in the situation of the vascular laminae, so as to avert 
their intervention in the experiment, the reparative horn had 
descended more than an inch, and in a more exuberant and 
prominent fashion than in the first described experiment. 
In addition to its more salient position, the horn also offered 
a difference in its physical characters ; it was excessively 
hard throughout, so that a hammer and chisel could scarcely 
make any impression upon it ; its outer surface was dry, 
without polish, often split longitudinally, and displayed its 
fibrous structure more markedly than in the other parts of 
the wall, while its internal face, examined after the animal 
had been destroyed and the hoof removed by maceration, did 
