EXTERNAL STRUCTURE. 



P7 



There is an evident intention in this division 

 o(* the head into so many bones. When the fetus 

 — 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 de- 

 posited in its stead. In flat bones, like those of 

 the head, this deposite takes place in the centre, 

 and rays or radiations of bone extend thence in 

 every direction. Then, by having so many bones, 

 there are so many centres of radiation ; and, con- 

 sequently, the formation of bone is carried on so 

 much the more rapidly, and perfected at the time 

 when the necessities of the animal require it. At 

 the period of birth, however, this process is not 

 completed, but the edges of the bones remain 

 somewhat soft and pliant, and therefore, in par- 

 turition, they yield a little, and overlap each other, 

 and thus, by rendering the birth more easy, they 

 save the mother much pain, and contribute to the 

 safety of the foal. Without a change in the form 

 of the head, from a compression and yielding of the bone of which it is 

 composed, the animal could not be born. 



The first of these bones, or the first pair of them, occupying the broad 

 expanse of the forehead, are called the frontal hones, a a. They are 

 united together by a most curious and intricate dove-tailing, to defend from 

 injury the brain, which lies beneath the upper part of them. Lower down, 

 and where the cavity of the nose is to be defended, their union is sufficient, 

 but far less complicated. The mechanism is here, as in every part of the 

 frame, and every part of the universe, wisely adjusted to the necessities 

 and wants of the animal. 



Few things more clearly indicate the breed or blood of the horse than 

 the form of the frontal bones. Who has not remarked the broad angular 

 forehead of the blood-horse, giving him that beautiful expression of intelli- 

 gence and fire, and the face gradually tapering from the forehead to the 

 muzzle ; and then compared it with the large face of the cart or dray-horse, 

 and the forehead scarcely wider than the face. 



At /, between the frontal bones, is the pit or cavity above the eye, and 

 by the depth of which we form some idea of the age of the horse. There 

 is placed at the back of the eye a considerable quantity of fatty substance, 

 on which the eye may revolve easily and without friction. In aged horses, 

 and in diseases attended with general loss of condition, much "of this fat 

 disappears ; the eye becomes sunken, and the pit above the eye deepens. 

 It is said that some of the lower class of horse-dealers puncture the skin, 

 and, with a tobacco-pipe or small tube, blow into the orifice, until the de- 

 pression is almost filled up. This operation is vulgarly called jnijing the 

 glims, and. with the aid of a bishopped tooth, will give a false appearance 

 of youth that will remain during many hours, and may deceive the 

 unwary, though the puffing may easily be detected by pressing on the part. 



These bones, however, are not solid, but a considerable portion of them 

 is composed of two plates receding from each other, and leaving numerous 

 anc. large vacuities or cells. These vacuities are called the frontal sinuses. 



