THE HEAD. 



33 



18 



3. Lumbar vertebras. The lumbar vertebrae are the strongest bones in the spine 

 and their bodies are nearly as thick as those of the larger domesticated animals. This 

 enormous development of the lumbar vertebrae in Man is related to his position as a biped. 

 In the fifth, the lower face of the body is cut very obliquely backwards and upwards, and 

 the transverse processes are more voluminous than those of the other lumbar vertebra. 



4. Sacrum. The sacrum is formed by the union 

 of five pieces. It is very concave from above to 

 below and before to behind. In becoming united 

 to the lumbar region, it forms a salient angle in 

 front, to which has been given the name of promon- 

 tory or sacro-vertebra] angle. The sacral spine is 

 continuous or interrupted, according to the subject ; 

 it is alway bifid inferiorly. 



5. Coccygeal vertebras. These are little bones 

 or flattened tubercles, four in number, rarely five, 

 and usually consolidated. The coccyx is conical in 

 shape. Its base shows two processes directed up- 

 wards, which are called the cornua of the coccyx. 

 Its summit is often deviated to the right or left. 



ARTICLE II. THE HEAD. 



The head is a large bony pyramid, elon- 

 gated from above to below, and quadran- 

 gular, suspended to the anterior extremity 

 of the spine ; it is in a direction varying with 

 the attitudes of the animal, but which we will 

 suppose, for convenience of description, to 

 be nearly vertical. It is formed of a great 

 number of particular bones, which are only 

 distinct from one another in very young 

 animals ; for well before the adult period is 

 reached the majority of the bones are united 

 and cannot be separated. 



The head is divided into two parts : the 

 cranium and the face. 



BONES OP THE CRANIUM. 



The cranium, or upper part of the head, 

 is composed of seven flat bones, five of 

 which are single : the occipital, parietal, 

 frontal, sphenoid, and ethmoid ; one only, the 

 temporal, is double. These bones circum- 1 

 scribe a central cavity, the cranial, which 

 communicates behind with the spinal canal, 

 and lodges the principal portion of the 

 nervous centres the encephalon. 



1. Occipital Bone. 



The occipital bone occupies the superior 



it supports 



extremity of the head, which 



from the anterior extremity of the spine. 



This bone is very irregular in it form, and 



is bent at a right angle in front and behind. 



It has an external and an internal face, and 



a circumference which brings it into contact 



with the adjoining cranial bones ; the latter is subdivided into two anterior 



HORSE'S HEAD; FRONT VIEW. 

 Occipital protuberance ; 2, Origin 

 of the mastoid crest ; 3, Parietal 

 bone ; 4, Saggital suture ; 5, Junc- 

 tion of the parietal and temporal 

 bones ; 6, Zygomatic arch ; 7, 

 Frontal bone ; 8, Frontal suture ; 

 9, Temporal fossa ; 10, Supraorbi- 

 tal foramen; 11, 12, Lachrymal 

 bone; 13, Malar bone; 14, Nasal 

 border of frontal bone ; 15, Nasal 

 bone; 16, Suture of nasal bones ; 

 17, Superior maxillary bone ; 18, 

 Infraorbital foramen; 19, Ante- 

 rior, or pre-maxillary bone ; 20, 

 Foramen incisivum ; 21, Incisor 

 teeth young mouth. 



