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 Com 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 

 neighborhood 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 Com, 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. 

 I This must be at the expense of the softer structures of the 

 foot. Accordingly, as the formation of pus increases, we 



