AS TO SOUNDNESS. 137 



the back of the tibiae, and so unduly press upon the 

 synovial sheath. In these cases the very least increase 

 of the oil in the sheath is shown. Where the hocks 

 are bent, and this lubricating sheath is not unduly 

 pressed between the os calcis and the back of the tibia 

 from their being well apart, should there be a large 

 thoropin, then the sheath must be much distended ; and 

 this is very likely owing to some injury to the tendon 

 of the flexon pedis perforans, which in bent hocks has 

 necessarily more stress thrown upon it. You will do 

 well to reject such as unsound. There are other ap- 

 pearances similar to thoropin, of which the most common 

 is bog-spavin, showing itself at the back of the joint as 

 well as in front, in which case unsoundness must be 

 your verdict, as it indicates a grave defect somewhere in 

 the joint. 



Curb is a disease due to strain upon the back of the 

 hock when the hind-foot is advanced far under the body, 

 as in the rearing and momentary poise during the pre- 

 paratory act of leaping a height, and in other conditions 

 such as fast trotting. The hocks may be so bent as to 

 protrude the feet beneath the body during ordinary 

 movement, in which case liability to curb is great. The 

 liability to curb is greatest, however, in " curby" hocks; 

 hence the name. " Curby " hocks may or may not be 

 the subjects of curb. If they are free, no one can tell 

 how long they will remain so. A "curby" hock is an 

 extremely defective hock, having its front lower bones 

 small, also the head of the large metatarsal small, and 



