26 STRUCTURE AND ECONOMY OF THE HORSE. 



The Vomer is a long thin bone, situated at the floor of tlio 

 nostrils, and running throughout their length ; its upper or 

 anterior part forms a deep groove, into which the cartihiginous 

 septum of the nostrils is closely imbedded, by which these are 

 separated into two distinct cavities. 



The Inferior Maxillary, or lower jaw bone, is formed of two 

 symmetrical halves, united at the inferior part by cartilage in 

 the young subject, but by bone in the adult. This united por- 

 tion forms deep and strong sockets for the inferior incisor teeth, 

 and posterior to this for the tusks : above this, each half sepa- 

 rates, and forms the bars of the mouth, as the space between the 

 incisor and the molar teeth is termed ; the bone then becomes 

 gradually wider and deeper, so as to form the sockets for the 

 inferior molar teeth : after which it diminishes in size, and ter- 

 minates in rounded extremities, which correspond to the glenoid 

 cavity in the temporal bone before described, thus forming the 

 maxillary joint. 



The bones which we have mentioned as composing the face 

 are none of them solid in their structui'e : but in order that the 

 requisite amount of surface should exist without too great weight, 

 they are most of them hollow ; and thus various sinuses are 

 formed, which are called after the bones in which they are found. 

 First we have i\\e froiital sinuses, which are situated between the 

 orbits; they are triangular in shape, their flat surface being 

 above, and two irregular ones below : they have infei'iorly blind 

 terminations, which are called the nasal sinuses, being in the 

 nasal bones ; and they communicate with the maxillary sinuses, 

 which are situated somewhat below and in front of them. 



The Maxillary are the largest of the sinuses of the head, ex- 

 tremely irregular in shape, and are formed principally by the 

 superior maxillary bones : their upper part is separated from the 

 orbit by the lachrymal and malar bones, which form their supe- 

 rior parts ; their lower extremity is blind, but above this there 

 is an opening into the chamber of the nostrils, besides the com- 

 munication before spoken of with the frontal sinus. 



There are other small sinuses, called the ISjjlicnoidal, the Eth- 

 moidal, and the Palatine, being found within the bones after 

 which they are called. The first of these is a single sinus, and 

 the last is situated between the palatine and the maxillary bones. 



These singular cavities are not found in the young subject, 

 but are gradually formed as the size of the head increases : one 

 im[)ortant purpose which they therefore serve is, to increase the 

 size of the head, without adding to its gravity. These sinuses 

 are often the seat of disease in glanders, when they often contain 

 matter, and are in an ulcerated state. 



The manner in which the head is connected to the body is 

 very remarkable, and demands particular consideration. In 



