20 SEATS AND SADDLES. 



sees, to the projecting position of the head and neck, 

 which are much heavier than the tail at the other 

 extremity. 



Looking now at the spinal column, the framework of 

 the back, on which the rider's weight is to be placed, we 

 perceive that, whilst the under line of the vertebrae is 

 nearly straight, although not quite horizontal, inclining 

 somewhat downwards towards the forehand, the spinal 

 processes of the first thirteen vertebras of the back 

 (dorsal vertebrae), reckoning from the point where the 

 neck is attached, incline backwards, whereas those of 

 the fifteenth, sixteenth, seventeenth, and eighteenth 

 dorsal, and the six lumbar vertebrae, incline forwards ; 

 the fourteenth dorsal vertebra, with its process, standing 

 perfectly upright, and forming, as it were, the keystone 

 of the arch thus presented. It is very obvious that this 

 inclination of the processes towards a central point is 

 intended to and does limit the motion of the back 

 downwards and upwards (i.e., vertically), so that, in 

 fact, this fourteenth dorsal vertebra becomes the centre 

 of motion of the horse's body the point about which 

 the several movements of the fore and hind legs are 

 performed with various degrees of rapidity, either 

 simultaneously or successively, and which constitute 

 the paces of the horse ; and this is further shown by 

 the distribution and points of attachment of the muscles 

 of the back and adjacent parts of the fore and hind 

 quarters. Putting, therefore, the progressive movement 

 of the animal out of the question as being equally 

 applicable to all its parts, the internal motion of the 

 several parts of the body increases in proportion to 

 their distance from the fourteenth vertebra ; and the 

 same is applicable to burdens placed on the horse's back, 



