172 DISEASES OF THE BONES AND AKTICULATIONS. 



time, before tlie death of the bone takes place, for the separa- 

 tion of more or less numerous portions of its surface. When 

 the entire periosteum has separated from the shaft, it carries 

 with it minute portions of the surface of the bone. Each of 

 these is covered on its external surface by the periosteum, on 

 its internal by a layer of granulations, the result of the 

 organized matter which originally filled the Haversian canals ; 

 the gradual enlargement and subsequent blending of which 

 ultimately allowed their vascular contents to combine, with the 

 layer of granulations just described, to form the separating 

 medium between the dead shaft and its minute living remnants. 

 These minute separated portions, after having advanced some- 

 what in development, appear, when carelessly examined, particu- 

 larly in dried specimens, to be situated in the substance of the 

 periosteum, and have been adduced, by the advocates of the 

 agency of that membrane in forming new bone, as evidences of 

 the truth of their opinions." 



The causes of necrosis totalis are ostitis and periostitis of a 

 violent form, brought about by galloping, jumping, or any other 

 cause of violent concussion ; it is situated in the long bones, 

 or in the os pedis in some cases of very acute laminitis, with 

 sloughing ; and a partial or total necrosis of this bone sometimes 

 results after neurotomy. 



The symptoms are violent pains, manifested by lameness, if 

 in the extremities, with swelling, at first doughy and elastic, 

 by reason of the effusion between the periosteum and bone, 

 and of the thickening of the periosteum itself; it presents no 

 distinct boundary when involving the whole length of the shaft. 

 The swelling gradually becomes harder as the process of ossifi- 

 cation goes on ; but at various parts, more especially towards 

 the lower portion of the bone, soft points can be detected in it, 

 attended eventually by fluctuation. These finally burst, and 

 discharge pus, which may at first be odourless ; but after the 

 abscesses have been open a short time, it emits that peculiar 

 fcetor characteristic of diseased or dead bone. If the abscesses 

 be examined with the probe, the bone will be found bare, and 

 perhaps loose. 



Treatment. — If a considerable length of a shaft is dead, some 

 time must be allowed for the consohdaticm of the capsule before 

 any attempt is made for the removal of the sequestrum, taking 



