46 



THE BONES. 



immediately directed backwards ; in the middle portion of this region these processes are very 

 obliquely directed downwards and backwards. 



3. Lumbar vertehrx. — The lumbar vertebrae are the strongest bones in the apine, and their 



bodies are nearly as thick as those of the larger domesti- 

 Fig. 2G. cated 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 vertebrae. 



4. Sacrum. — The sacrum is formed by the union ot 

 five pieces. It is very concave from alx)ve 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 Xheuameo^ promontvry ox sacro-vertebral angle. 

 The sacral spine is continuous or interrupted, according 

 to the subject; it is always bifid inferiorly. 



5. Coccygeal vertebras. — These are little bones or flat- 

 tened tubercles, four in number, rarely five, and usually 

 consolidated. The coccyx is conical in shape. Its base 

 shows two processes directed upwards, which are called 

 the cornua of the coccyx. Its summit is often deviated 

 to the right or left. 



Article II.— The Head (Fig. 26). 



The head is a large, bony, quadrangular 

 pyramid, elongated from above to below, sus- 

 pended by its base to the anterior extremity of 

 the spine. Its direction varies with the atti- 

 tudes of the animal, but we will suppose it, 

 for convenience of description, to be nearly verti- 

 cal. 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. 



house's head (front view) 



1, Occipital tuberosity; 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, supra-orbital 

 foramen; 11, 12, lachrymal bone; 

 13, malar bone ; 14, nasal border of 

 frontal bone ; 15, nasal bone ; 16, 

 suture of nasal bones; 17, super- 

 maxillary bone ; 18, infra-orbital 

 foramen ; 19, anterior, or pre- 

 maxillary bone ; 20, foramen in- 

 cisivum ; 21, incisor teeth (young 

 mouth). 



Bones of the C rani am. 



The cranium, or upper part of the head, is 

 composed of seven flat bones, five of which are 

 single : the occipital, parietal, frontal, sphenmd, 

 and ethmoid; one only, the temporal, is double. 

 These bones circumscribe a central cavity, the 

 cranial, which communicates behind with the 

 spinal canal, and lodges the principal portion of 

 the nervous centres — the brain. 



1. Occipital Bone (Fig. 26, 1). 



The occipital bone occupies the superior extremity of the head, which it 

 supports from the anterior extremity of the spine. This bone is very irregular 

 in its form, and is bent at a right angle in front and behind. It has an external 



