DISEASES OF THE SKELETON. 399 



affected part undergoes extensive disorganisation. When 

 a number of fragments of bone are separated in a com- 

 minuted fracture these act as foreign bodies^ and necrose 

 through defective blood supply. When this is the case 

 the larger portions may be surgically removed, and when- 

 ever a small amount of necrosis is present hydrochloric acid 

 dressings will prove useful by breaking up the bony 

 structure. One of the most frequent seats of necrosis is 

 the pastern bones in cases of foul. In cases of ostitis 

 poultices should be applied, and the parts freely fomented 

 and as thoroughly rested as possible. Besides a laxative 

 dose no constitutional treatment is generally required. 



Peeiositis and Inflammation of the Outer Lamina of 

 A Bone result from injury and, occasionally, from rheu- 

 matism. The membrane becomes thickened, and some- 

 times much congested, and an exudation of lymph beneath 

 it occurs, which becomes converted into bone. The pro- 

 cess is painful, and sometimes requires to be relieved by 

 ■periosteotomy. This operation does not seem to have 

 been used in cattle practice. A case of diffused meta- 

 tarsal periostitis, by Professor Walley, may be read in the 

 ^Veterinary Journal,' 1880, vol. i^ 126. It was a com- 

 plication of arthritis of the hock and fetlock, and led to 

 encasement of the upper three fourths of the metatarsus 

 by a bony layer. Chronic cases of ostitis and periostitis 

 are sometimes benefited by a blister. 



Exostosis — Bony Growth from Bone — results in most 

 cases from periostitis. In the first place it is simply 

 lymphy material thrown out, but later earthy matter is de- 

 posited in it, and this in process of time becomes converted 

 into true bone. Callus thrown out round a fracture has 

 much the same nature, but is specially arranged in relation 

 to the injured bone. The most remarkable growths of this 

 nature seen in the ox are those dense outgrowths from the 

 petrous temporal bone which extend into the cranial 

 cavity and cause absorption of the brain ; they attain an 

 immense size and weight, and become closely moulded 

 against the cranial walls in such a way that often they 

 present a lobulated appearance, and have ramifying grooves 



