THE HEAD. 



47 



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

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

 the brain, and thus comiected 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 oi' secretion and of nutrition, atd 

 the repair and the welfare of the frarae generally. 



The Head. — The following cut represents the head of the 

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

 and the boundaries of each bone clearly marked by the sutures 

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

 bones. 



a a Tlie frontal bones, oi' bones of the forehead. 



b b The supra-orbital foramina or holes above the 

 oroit, through which the nerves and blood- 

 vessels supplying the forehead pass out. The 

 small hole beneath receives the vessels which 

 dip into and supply the bone. 



C c The parietal bones, or walls of the skull. 



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



e e The zygomatic, or yoke-shaped arch. 



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



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

 of the head. 



h k The orbits containing and defending the eye. 



i i The lachrymal bones belonging to the convey- 

 ance of the tears from the eyes. 



j j The nasal bones, or bones of the nose. 



k k The malar, or cheek-bones. 



1 1 The superior maxillary, or that portion of the 

 upper jaw containing the molar teeth or 

 grinders. 



mm 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 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 the point of union 

 between the superior and inferior maxillaries. 

 o The upper incisor or cutting teeth. 

 p The openings into the nose, with the bones 

 forming the palate. 



The ethmoid and sphenoid bones will be better seen ii the cut 

 Fig. 3. 



There is an evident intention in this division of the head into 

 so many bones. When the fcutus — the unborn foal — first begins 

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

 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 



