MORBID CONDITION OF CARTILAGE. 223 



When none of these results have taken place, the process 

 of destruction is arrested and limited by a deposition into 

 the bone of a peculiarly hard, calcareous material — the 

 porcellaneous deposit — which fills up the cavity, and blocks 

 the cancelli and canals of the bone, and by its smooth and 

 polished surface makes up to some extent for the want of the 

 cartilage. 



In old horses the cartilage of incrustation is exceedingly thin, 

 and in some cases it wdll be found converted by ossification 

 into the above-mentioned ivory or porcellaneous deposit. This 

 deposit is exceedingly dense, and derives its hardness from the 

 Haversian canals being filled up by additional laminae. 



The depressions or cavities termed sulci, which are found in 

 many close-fitting joints, as the elbow and true hock joints, 

 must not be mistaken for a diseased condition. They are merely 

 cavities for storing synovia. 



TRAUMATIC INFLAMMATION OF JOINTS. 



An open joint, when occasioned by puncture or incision, is 

 not at first (if unassociated with fracture) attended by severe 

 local or constitutional disturbance ; but at the end of a period 

 varying from two to ten days pain comes on, and spreads over 

 the joint, w^hich soon presents a considerable amount of swelling 

 and tension. The swelling is at first tense, but elastic ; how- 

 ever, it soon becomes hard and unyielding, and accompanied 

 by great constitutional disturbance, the pulse rising in frequency, 

 becoming hard and wiry in its character, and the animal evincing 

 acute and agonising pain by partial tremors and sweats upon 

 his body. In fact, all the constitutional symptoms indicate a 

 state of great irritability. The lameness is excessive. The 

 animal is scarcely able to put its foot to the ground, whilst at 

 the same time the pain causes it to keep it in an almost con- 

 tinual state of motion. An injury not at first penetrating the 

 joint may do so in the course of three or four days, by sloughing 

 of the tissues around it, these having been destroyed but not 

 removed by the violence of the injury. 



The discharge of synovia may be very trifling for some days 

 after the accident ; but it gradually increases as the inflamma- 

 tion advances, is thin in its consistency, and mixed with flakes 



