WOUNDS 233 
portions of the secreting layer of the keratogenous mem- 
brane are destroyed, or perhaps only temporarily prevented 
from fulfilling their horn-producing functions, then corre- 
sponding cavities in the horn are the result (see Fig. 109). 
(b) Purulent Arthritis.—Only too readily the pus so 
formed tends to penetration of the articulation and the 
causation of an incurable arthritis (see Chapter XII.). 
(c) Necrosis of the Extensor Pedis.—This may arise either 
as a result of spreading purulent infection of the coronary 
Fig. 109.—-Mrs1aL SECTION oF A HOOF ILLUSTRATING THE CONDITIONS 
; FOLLOWING UPON CORONITIS. 
a, Cavity in the horn of the wall; b, enlargement of the coronet and the 
horn of the wall following subcoronary suppuration ; vc, cavity in the 
wall following purulent inflammation of the sensitive lamine ; d, hollow 
in the horn of the sole consequent upon suppuration of the sensitive sole. 
cushion, or as a result of direct injury immediately over 
it. The close relation of the terminal portion of this 
tendon with the pedal articulation, and the incomplete pro- 
tection from outside injuries here afforded to the joint by 
the horny box, sufficiently points out the gravity of the 
condition. 
(d) Penetration of the Articulation—This also may be a 
result either of. the inroads made by pus, or of an actual 
wound. When occurring from the latter, it is seen more 
often than not in the hind-foot, being there caused by the 
