THE SPINAL CORD. THE NERVES. 19$ 



its hinder end laps over it. A deep groove runs along the 

 cerebrum from front to back and nearly cuts it in two. 

 Its halves are named the right and left cerebral hemi- 

 spheres, and their surfaces are not smooth but are marked 

 by numerous crooked furrows, with ridges between (Fig. 

 53). The ridges are known as the convolutions. 



CIA 



FIG. 53. The brain from the left side. Cb, the cerebrum, or, rather, the left 

 cerebral hemisphere; Cbl^ the cerebellum; Mo, the medulla oblongata. 



6. The Spinal Cord is nearly round, and is about three 

 quarters of an inch across and seventeen inches long. 

 It does not reach as far as the lower end of the back-bone. 



7. The Nerves start from the brain and spinal cord. 

 Twelve pairs (cranial nerves] are attached to the brain and 

 go out through holes in the skull; thirty-one pairs (spinal 

 nerves) spring from the sides of the spinal cord, and pass 

 out between the vertebrae. 



6. Describe the spinal cord. How far does it reach ? 



7. Whence do the nerves start ? What is said of the cranial nerves ? 

 Of the spinal? Of the nerve-fibres? Describe the branching of 

 nerves, 



