OSTITIS. 153 



The outer surface of the iuflamed bone presents a spongy 

 pvppearance, from a deposition of new bone ; the periosteum is 

 thickened, and in the more acute cases it is detached from the 

 bone, which, when exposed, has a white and smooth appearance, 

 with hardly any change in its structure, the diseased action 

 having been too rapid to allow it to open out. 



When the inflammation is of the chronic form, the patholo- 

 gical changes occur more slowly, and when different parts of a 

 bone are affected, new osseous material is deposited here and 

 there, giving the bone an irregularity of shape, as in multiple 

 splints. 



A very moderate degree of inflammation in the outer lamella 

 of bone, produces a gelatinous, dark red exudation, which gradu- 

 ally changes its colour to bluish-red and reddish-white, and at 

 length becomes quite white ; at the same time, passing from its 

 original gelatinous condition, it forms a coagulum, like the white 

 of an egg, then becomes a soft flexible cartilage, and finally 

 reddish- white succulent bone. In this state it invests the bone, 

 and constitutes, according to its quantity, either a white, porous, 

 and scarcely perceptible film, or a thicker layer, that resembles 

 felt or velvet. The periosteum appears at first injected, bluish- 

 red, infiltrated, and decidedly swollen, and generally has but a 

 loose connection with the exudation. The ossified exudation 

 unites with the surface of the bone, and either forms uninter- 

 ruptedly an addition to the compact wall, or is connected with 

 it by a spongy layer (diploetic). The inflammation may recur in 

 the exudation at any period of its existence, leading to a corre- 

 sponding increase in its size. 



Such, then, are the general outlines of the various changes that 

 occur consequent upon inflammation of bone. 



OSTITIS AND PERIOSTITIS OF THE METACARPAL BONES, OR 

 " SORE SHINS." 



This is a form of disease affecting the metacarpal bones of 

 young horses, particularly race-horses under four years old, and 

 is due to the fact that they are called upon to perform an 

 amount of work at an age when the condition of their bones is 

 totally unfit to bear it. 



The bones of the young, being in a state of development 



