770 
DISEASES OF THE FOOT. 
grey or blackish material, termed “ horn pus,” at the coronet or heels, 
and the absence of marked swelling, point to the superficial nature of 
the attack. 
(2) Pododermatitis parenchymatosa affects the corium or subcutis, and 
is generally associated with disease of the surface, from which it may 
originate, though it also results from deeper injuries, like pricks, &c. 
The podophyllous membrane, or its subcutis, forms the seat of acute 
inflammation, accompanied by exudation ; suppuration almost always 
occurs, the pus being precisely similar in character to that formed in 
other portions of the skin, and appearing thick, yellow, and creamy, 
while, if its formation is accompanied by necrosis, it may be offensive. 
The character of the discharge, in fact, is a very valuable indication for 
diagnostic purposes. When white, yellowish or creamy, the keratogenous 
membrane is evidently suppurating, or may even be undergoing partial 
gangrene ; if reddish, or of the colour of wine lees, and stinking, it indicates 
diffuse gangrene of the membrane, which, again, is often accompanied 
by necrosis or caries of the os pedis ; when yellowish, viscous, “ curdled,” 
or containing fibrinous flocculi, and especially if escaping by a sinuous 
opening in the coronet or sole, it points to synovitis of the lower sesamoid 
sheath, or to arthritis of the pedal-joint. The significance of these 
peculiar characters in the pus is again controlled by the degree of pain 
and general disturbance. 
The attack may terminate either in resolution, abscess formation, or 
necrosis. The first rarely happens. Much more frequently an abscess 
forms, similar to those in other positions, and leads to either—necrosis 
of the sensitive sole, purulent cellulitis, or septicaemia. 
Necrosis usually depends on inoculation with particularly virulent 
infectious substances, though it is favoured by the position of the sensi¬ 
tive laminae and sole between the unyielding horn on the one side and 
the os pedis on the other, which causes any considerable swelling to be 
followed by severe compression and interference with circulation. The 
common occurrence of necrosis at certain times shows that infection plays 
an important part, though in winter the action of cold may also have a 
certain action. During outbreaks of gangrenous dermatitis one often sees 
necrosis, the dangerous consequences of which are aggravated by the 
difficulty with which the dead tissue separates, and by the readiness with 
which putrefactive products are absorbed and diffused in neighbouring- 
structures, leading to inflammation of the laminae or sole, and not 
infrequently to separation and loss of the hoof. Such a termination is 
preceded by excessive pain, fever, and extensive separation at the coronet. 
If the first point involved is one where the sensitive structure lies closely 
in contact with the bone (as is the case over the greater part of the sole 
and wall), necrosis almost always attacks the os pedis. 
