ELEMENTS OF HIPPOLOGY. 67 



pressure off the tongue, when the bit is in use, and to localize it 

 on the bars. The port, when the bit is at rest, lies on the tongue. 

 When the bit is used, the port revolves upward and forward, 

 away from the tongue, with the result that the insensitive tongue 

 is freed from its influence. At the upper ends of the cheek- 

 pieces are rings for the attachment of the curb-chain. This chain 

 should be so adjusted that, when it is brought into use, it will lie 

 in a smooth depression of the jaw-bone, called the chin-groove. 



Figure 49. — The Under Side of the Lower Jaw-Bone. 



The chin-groove is the rounded portion of the jaw-bone 

 just forward of the angle of the V. In health, it is smooth and 

 rounded, and admirably fitted to receive the pressure of the 

 curb-chain without injury to itself. The two branches of the 

 jaw-bone are very thin and sharp on the under side, where they 

 unite to form the chin-groove, and it is, as will be seen, highly 

 important that the curb-chain should fit into the chin-groove, 

 and not lie on these sharp bones. 



There should be loops on the posterior edges of the cheek- 

 pieces, half way from the rein-rings to the mouthpiece, to attach 

 the lip-strap to. This strap is often necessary to prevent the 

 horse from getting the lower branch of one of the cheek-pieces 



