THE CAVITY OF THE SKULL. 



27 



tebrce; in the back (dorsum), 2, twelve dorsal vertebrce, from * to * ; 

 in the loins (lumbi), 3, five lumbar vertebrae ; making in all twenty- 

 four movable vertebrae. Next below these are five sacral vertebrae, 

 consolidated into the one mass called the sacrum, 4 ; and below this 

 are three or four little bones, .called the coccygeal vertebrae, 5, forming 

 the coccyx (cuckoo's bill) : these constitute the immovable vertebrae. 

 It should also be here stated that the bones of the head are considered 

 as consisting of specially modified bony elements, called cranial ver- 

 tebrae. Each of the vertebrae, as shown in Fig. 11, in which a, c, and 

 e, represent the right side, and b, d, and /, the upper surface of a 



Fig. 9. 



Fig. 9. A section vertically through the middle of the head and neck. The hollow of the skull, lined by 

 the membranes called the dura mater and the arachnoid, is marked c. The membranous partition, called 

 the falx, is marked/; its hinder part being connected below with the right half of the tentorium. The 

 spinal canal, s, leading from the cranial cavity, is seen lower down still. The cut ends of certain cranial 

 nerves are also shown. Along the upper edge of the falx, close to the bone, is a large channel or venous 

 sinus. The sections of the cranial, facial, and spinal bones are also seen. The right nasal cavity is marked 

 n. Below it is the cavity of the mouth, containing the tongue; these two cavities are separated by the 

 hard and soft palate. Both of them open behind into the throat cavity or pharynx, p, which again leads 

 ddwnwards into the gullet or oesophagus, o, immediately in front of the spine. At the root of the tongue 

 is seen the cut surface, h, of the byoid or lingual bone ; suspended to this is the larynx, I, the hollow carti- 

 laginous organ in which the voice is produced, and through which the air passes from the pharynx into 

 the windpipe, t, which is the open tube running down the front of the neck from the larynx. The divided 

 bodies of the vertebrae are marked v. (After Bourgery.} 



characteristic cervical, dorsal, and lumbar vertebra, consists of a solid 

 part called the body, which is turned forwards, and which is strongly 

 tied to the bodies of the adjacent vertebrae ; secondly, of an open ring 

 behind this ; and thirdly, of three principal projections or processes, 

 one backwards, called the spinous process, from the whole series of 

 which the backbone is called the spine, and two lateral ones called the 



