DISEASES FROM FAULTY CONFORMATION 195 
When, as is sometimes the case, layers of horn that are 
stained are found alternated with layers that are healthy, 
then we have evidence that the cause of the corn, whatever 
it may be, is not in constant operation. 
Similar indication of the age of the injury is also afforded 
by the colour of the lesion. 
A stain that is deep red is proof that the injury is com- 
paratively recent. 
A distinct yellow or greenish tinge, on the other hand, is 
evidence that the injury is an old one. 
In the Moist Corn we have, in addition to the blood ex- 
travasation, the outpouring of the inflammatory exudate. 
In the most superficial layer of the horn this may not be 
noticeable. As one cuts deeper into the sole with the knife, 
however, it will be found that the lower layers of horn are 
more or less infiltrated with the discharge. This gives to 
the horn a soft consistence, a yellow appearance, and a 
touch that is moist to the fingers. 
With the accompanying inflammation the cells in the 
neighbourhood of the injury are enfeebled and their normal 
functions interfered with. We may thus expect a corre- 
sponding interference with the growth of horn. This is 
exactly what happens, and as one cuts deeper still into the 
horn a point is finally reached when a well-marked cavity 
is encountered. A pale yellow and usually watery exudate 
fills it. This cavity points out the exact spot where the 
force of the injury has been greatest, where death of certain 
cells of the keratogenous membrane has resulted, and where 
the natural formation of horn has for a time been sus- 
pended. 
In the Suppurating Corn, as in moist corn, we have 
pathological changes due to the tissue reaction to the 
injury, plus the addition of pus organisms. Confined 
within the horny box we have a discharge that, by reason 
of the living and constantly multiplying elements it con- 
tains—the pus organisms—is always increasing in bulk. 
This must be at the expense of the softer structures of the 
foot. Accordingly, as the formation of pus increases, we 
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