888 INFLAMMATION OF STRUCTURES ENCLOSED BY THE HOOF. 



horn of the white line and sole. Their commonest seat is 

 between wall and bar. 



A light bruise causes exudation at the surface of the corium, 

 forming the sensitive laminae and papillae. After more severe 

 bruises blood-vessels are ruptured, blood poured out between 

 the corium and growing horn, is absorbed by the latter and 

 gives rise to the above described discoloration. The coloured 

 portions are carried downward by the continued growth of 

 horn, until finally they reach the ground surface. It is, there- 

 fore, clear that a corn is never visible at the time of its pro- 





Fig. 364.— Cross section of the horny and sensitive walls from a case of contracted heel. 

 Magnified 26 diameters, a, horny wall ; b, horny laminae ; b', their foldings ; c, showing 

 change in direction of secondary laminai ; d, sensitive wall. 



duction, and cannot be detected until the hoof has been ' cut 

 out.' Corns may be situate in the sensitive wall of the heel, 

 the sensitive sole coverino- the corner of the heel and the 

 sensitive bar, for which reason, wall, sole, and bar corns have 

 been differentiated. They are rare in unshod horses. The 

 front feet, and especially the inner heels, are their commonest 



