THE I/EVER, THE BIT AND CURB, ETC. 177 



for these is three-fourths the height of the upper cheek, 

 or about 1^ inch. 



The above length of curb applies to what is really 

 employed between the two hooks, but it is usual to 

 have one reserve link at the off side, and two of these 

 at the near one, which latter are convenient, or rather 

 indispensable, for catching a proper hold of the curb 

 when being hooked on. 



We now have gone step by step through the several 

 details connected with the bit considered as a lever 

 namely, its cheeks, and the curb with its hooks, which 

 represent the fulcrum or prop. There remains the 

 mouth-piece, which is of equal, if not greater, im- 

 portance, as the part of the instrument through which 

 the immediate impression is made on the mouth, and 

 therefore generally placed in the foreground by writers 

 on this subject. It appeared, however, to us to be a 

 matter of great importance to make it perfectly clear, 

 in the first place, that the entire action of the bit 

 should be concentrated on the mouth-piece, that the 

 operation of the curb should be confined wholly to 

 the function of a painless fulcrum, and that there are 

 certain narrow limits to the size of the upper and lower 

 bars which form the cheeks of the instrument. The 

 form and proportions of the mouth-piece must be de- 

 duced wholly from the interior conformation of that 

 part of the mouth on which it is intended to act, and 

 these are, the tongue in the centre and the bars of the 

 mouth on each side. It has been already pointed out 

 that the relative hardness or softness of the mouth, so 

 far as this depends on the conformation of this organ 

 itself is a consequence of the greater or less thickness 

 of the tongue, and the greater or less sharpness and 



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