THE VERTEBRAL CANAL. 



29 



white, stalk-like prolongation into the spinal canal, which is named 

 the spinal cord, c. It extends down only to the first lumbar vertebrae, 

 <?'. The brain and spinal cord are the great centres of the nervous 

 system. From the base of the former, and from the sides of the latter 



Fig. 11. 



Fig. 11. Two different views of a characteristic cervical, a dorsal, and a lumbar vertebra, a, right side, 

 and 6, upper surface of a middle cervical vertebra ; c and rf, similar aspects of a middle dorsal vertebra ; 

 and e and/, the same of a middle lumbar vertebra. These figures show the thick or anterior part or body 

 of the bones, their rings, their backward or spinous processes, their lateral or transverse processes, and 

 their articular processes. The differences in size and form between each of these parts in the different ver- 

 tebrae are also shown. (From Nature.) 



(see Fig. 62), are given off the white cords, called nerves, which, pass- 

 ing through special openings in the base of the skull (see the cut ends 

 of several in Fig. 9), or through the inter vertebral apertures between 

 the vertebrae (see Fig. 10, especially in the loins), branch out into 

 every part of the body (see Fig. 64). The nerves form the peripheral 

 part of the nervous system. The brain and spinal cord are closely 

 invested by a vascular membrane, the pia mater, over which is a layer 

 of the arachnoid continuous along the roots of the nerves with that 

 lining the dura mater. 



The part of the entire skull which we call the face also has certain 

 hollows or recesses in it, which may be regarded here as cavities for 

 the lodgment of organs. Of the bones which are consolidated together 

 below the cranium to form the face, some are seen on the surface, viz., 

 the cheekbones, Fig. 8, 6, or malar bones (rnalce, the cheeks), which 

 assist in forming the margins of the eye-sockets ; the two upper jaw- 

 bones, 4, or superior maxillary bones (maxillae, the jaws), which, 

 together, contain the upper teeth, form the sides of a great notch 

 which corresponds with the nose, and also ascend to complete the 

 margins of the eye-sockets ; the two little nasal bones (nas, the nose), 

 which complete the upper boundary of the nasal cavities, and form the 

 bridge of the nose ; and, lastly, the lower jaw-bone, or inferior maxil- 



