372 



HEALTH AND DISEASE 



Fig. 393. Keratoma or Horn Tumour 



Notch or groove in the pedal bone resulting from pressure 

 of Keratoma. 



KERATOMA HORN TUMOUR 



A tumour composed of 

 horn sometimes forms on the 

 internal face of the hoof, from 

 which it projects inwards, and 

 by continued pressure imbeds 

 itself in the substance of the 

 pedal or foot bone, some of 

 which it causes to be ab- 

 sorbed. These growths may 

 be elongated, ovoid, or cone- 

 shaped. They mostly occur at 

 the toe, but, rarely, also appear 

 at the coronet, from which they 

 extend downwards towards 

 the lower border of the foot. 



Keratoma is produced by an abnormal growth of horn from the laminae 

 or papillae of the vascular tissues by which the hoof is secreted. 



Causes. These 



growths have their origin 

 in some injury or irrita- 

 tion of the horn-secreting 

 structures. A blow or 

 tread on the coronet may 

 be the exciting cause, 

 but more commonly it 

 would seem to have some 

 connection with injury 

 done to the toe, which 

 is generally believed to 

 be inflicted by too much 

 force being used in ham-: 

 mering down the toe 

 clip. Injury by a nail 

 driven too near the quick 

 may also be the starting- 

 point, or it may follow a 

 crack in the hoof. How- 

 ever produced, there is evidently a chronic state of congestion excited in 

 the horn-forming structures at the seat of the morbid growth. 



Fig. 394. Keratoma or Horn Tumour 

 Transverse section of foot, showing Keratoma (a) in situ. 



