THE NECK, THE HEAD, ETC. 135 



height above the tusk ; but as mares and even many 

 geldings have no tusks, this is a very clumsy method, 

 which is supj)lemented in practice by hanging the bit 

 in the horse's mouth nearly as high as the angles of 

 the lips will allow it to go. This is about equally wise 

 as it would be to put the lock of a gun somewhere near 

 the vent — an inch or two higher or lower does not 

 matter. As far as the bit itself is concerned, half an 

 inch, or even a full inch, higher or lower, would not 

 make much difference in its action ; but, as we shall 

 presently see, the curb has one fixed position in the 

 chin-groove, and this governs the whole an-angement. 



There are three dimensions of the interior of the 

 horse's mouth which must be accurately ascertained 

 before attempting to fit him with a proper bit, in addi- 

 tion to certain details connected with the tongue. The 

 first, and a veiy important one, is the transversal width 

 of the month from side to side, measured at the same 

 height as the chin-groove, and including the thickness 

 of the lips — that is to say, from the point d, fig. 12, 

 to the corresponding point at the offside.* This gives 

 the width of the mouthpiece, which must be made to 

 fit exactly, as, if too narrow, the lips are subject to 

 injury and their being displaced so as to cover the 

 bars, thereby neutralising the action of the whole 

 instrument ; whereas, if too wide, it slips from side to 

 side, and displaces what is termed the port — the curved 

 portion of the mouthpiece intended to moderate the 

 pressure on the tongue — from its proper position : it 

 also determines the length of the curb. The second 

 dimension is the width of the channel in which the 



* The proper mode of ascertaining all these dimensions accu- 

 rately will be stated further on. 



