HEAD IN GENERAL. 91 



requires a mean position of contact of the articular surfaces. Finally, 

 the reversing of the neck, which is the consequence, renders the inser- 

 tion of the muscles, now approaching the perpendicular direction, less 

 defective, and at the same time increases the power of the mechanical 

 action of the nuchal ligament (Fig. 29, B). 



It is sometimes impossible to prevent the animal from holding the 

 head in this position. The remedy consists in the use of ihe_martin- 

 gale, a strap of leather of suitable length extending from the bit to- 

 the girth of the saddle. This apparatus is frequently added to the 

 harness simply as an ornament. In sadclle-horses this faulty direction 

 can also be prevented by the use of a martingale with rings at its 

 extremity, through which the reins pass, and which act as a pulley to 

 keep the latter in their proper position, and thus prevent the elevation 

 of the head. 



When the head is held in the vertical position the centre of 

 gravity is carried backward and downward. The line of gravitation 

 approaches the centre of the base of support, whence ensues a state of 

 stable equilibrium, more difficulty in displacing the centre of gravity, 

 and less quickness of movement. This position of the head is objec- 

 tionable in driving-horses and in running-horses, whilst in draught- 

 horses it is not. 



A vertical head is always accompanied by an arched or swan neek> 

 the appearance of which is agreeable to the eye. Besides having the 

 defect which we have indicated, the head is not in a good position for 

 seeing distinctly objects beyond a certain distance. The field of vision 

 does not extend far enough ahead to enable the animal to avoid obsta- 

 cles which may be in his path. Also, like those which carry the head 

 in extension, he is apt to stumble and fall, but for opposite reasons. 



In this direction of the head the incidence of the extensors is 

 acute and that of the flexors obtuse (Fig. 30, A). Here again the 

 neck is incurvated or arched to preserve the normal relation of the 

 articular surfaces of the occipito-atloid articulation and render at the 

 same time the insertion of the muscles more perpendicular to the arm 

 of their lever (Fig. 30, B). This vertical direction is less objectionable 

 in the saddle-horse than in any other. In horses which present it the 

 steps are short and the flexion of the knees (knee-action) is more 

 marked. They are more sensitive to the bit, and quite manageable 

 if the conformation be not exaggerated. 



When excessive, however, it constitutes a serious defect, as when 

 the head is oblique from above to below and from before to behind, and its 

 inferior extremity approaches the sternum. The effect of the backward 



