OBSTINATE CHARACTER OF KER ATOM ATA. 



399 



wider. The keratoma thus produced gradually occupies the 

 formerly empty space, and in its turn may lead to partial 

 atrophy (pressure atrophy) of the os pedis. 



Keratomata may be caused by chronic inflammation un- 

 accompanied by suppuration. The cavity in the os pedis 

 corresponds in form and extent with the keratoma. 



Symptoms. — Horn tumours do not invariably produce lame- 

 ness, but, when lameness is present, pain, increased warmth and 

 pulsation of the digital arteries may usually be detected. The 

 growth can only be removed after it reaches the bearing 

 surface. The white line is then distorted at some part of its 



Fig. 377.— a piece of the toe wall removed, together with keratoma, a, coronary margin ; 

 b, plantar margin ; c, keratoma ; d, depression containing pus. 



course, describing a semicircle around the horn tumour, which 

 appears at the ground surface as a waxy-looking body. The 

 new growth occasionally undergoes degeneration, producing a 

 depression of varying depth, with dark coloured walls, from 

 which a greyish-black pus is sometimes discharged. 



Causes. — Chronic inflammation of the sensitive wall conse- 

 quent on bruises, pricks in shoeing, clefts in the horn, corns, or 

 treads. 



The prognosis is unfavourable whether lameness exists or 

 not. Under any circumstances lameness is probable and liable 

 to recur even after removal of the growth. 



Treatment. — When suppuration has seriously affected the 



