THE HEAD. 



47 



whicJ all sensation is referred or carried, ai.d from which all 

 voluntary motion is derived — the spinal cord, a prolongatioi of 

 the brain, and thus connected with sensation and voluntary mo- 

 tion, governing all the involuntary motions of the frame, and by 

 power from which the heart beats, and the lungs heave, and the 

 stomach digests ; and one other system of nerves — ^the ganglionic 

 — presiding over the functions of secretion and of nutrition, aid 

 the repair and the welfare of the frame generally. 



The Head. — The follovidng cut represents the head of Iho 

 horse divided into the numerous bones of which it is composed, 

 and the boundaries of each bone clearly marked by the sutures 

 which connect it with those around. It is composed of nine 

 bones. 



Fig. 2. 



a a The frontal bones, or bones of the forehead. 



b b The supra-orbital foramina or holes above the 

 oroit, throQgb which the nerves and blood- 

 vessels supplying the forehead pass out. The 

 SDiall hole beneath receives the vessels which 

 dip into and supply the bone. 



c e The parietal bones, or walls of the skuU. 



d d The temporal bones, or bones of the temples. 



c e The zygomatic, or yoke-shaped arch. 



// The temporal fassa, or pit above the eye. 



g' g- The occipital bone, or bone of the hinder part 

 of the head. 



k k The orbits containing^ and defending the eye. 



t i The lachrymal bones belonging to the convey- 

 ance of the tears from the eyes. 



jj The nasal bones, or bones of the nose. 



% k The malar, or cheek-bones. 



/ / Tbe sujferior maxillary, or that portion of the 

 upper jaw containing tbe molar teeth or 

 grinders. 



m m The infra-orbital foramen — a hole below the or- 

 bit, through which pass branches of nerves 

 and blood-vessels to supply the lower part of 

 the face. 



« n The inferior maxillary, the lower part of the 

 upper jaw-bone — a separate bone in quadru- 

 peds, containing the incisor or cutting teeth, 

 and the upper tushes at tbe point of union 

 between the superior and inferior maxillaries. 

 o The upper incisor or cutting teeth. 

 p Tbe openings into the nose, with the bones 

 forming the palate. 



The ethmoid and sphenoid hones will be better seen ii ihe cu> 

 Fig. 3. 



There is aa evident intention in this division of the h^ad into 

 .so many bones. "V\Tien the foBtus — ^the unborn foal — ^first begins 

 to have life, that which afterwards becomes bone, is a mere jellv- 

 like substance. This is gradually changed into a harder material 

 — cartilage ; and, before the birth of the animal, much of the 

 cartilage is taken away by vessels called absorbents, and bone 



