THE NERVES. 361 



whole thickness ; according to Valentin, the nervous fibres of the 

 flexor muscles are situated in the anterior columns of the spinal 

 cord and pass over those of the extensor muscles in the posterior. 

 The motor and sensitive nerves of the viscera pass along in the 

 spinal marrow (See JV. sympathicus). 



2. The brain sends off twelve pairs of nerves. These are, 

 partly, nerves of sensation (and of the senses), partly nerves of 

 motion, and partly of both together (mixed nerves). They are 

 abstractedly of the three nerves of the higher senses (for smell, 

 sight, hearing), which may be considered as parts of the brain, in 

 accordance with the spinal nerves, and the skull has been regarded 

 as consisting of three vertebrae. Accordingly there might be an 

 anterior (n. oculo-motor, abducem trigeminus) and a posterior in- 

 tervertebral nerve of the skull (N. glossopharyng., vagus with 

 accessorius and hypoglossus). We cannot, however, refer to, in 

 all, an anterior and posterior root. They arise from the posterior 

 part of the basis of the brain. 



The hemispheres of the cerebrum, carp, callosum, hypophysis 

 and pineal gland, are the means neither of motion nor sensation ; 

 it appears, accordingly, as if the mental functions (thought) were 

 dependent upon them. 



In the cerebellum the nerves of the large intestines, of the blad- 

 der and organs of generation, terminate; in the optic tubercles and 

 striated bodies those of the stomach and small intestines ; in the 

 corpora quadrigemina (by going through Pans Varolii) the nerves 

 of the trunk. 



The vessels of the central parts are very fine, and consist of the 

 primary vascular coat only ; they form close rete in the gray, but 

 are more sparingly diffused in the white substance. They spread 

 out on the surface in the^'a mater (see after), and from here sup- 

 ply the substance (and from the processes which the last sends into 

 the cerebral cavities, as plexus choroidei). The arteries quickly 

 pass into capillary vessels. Lymphatic vessels are not known in 

 the substance, but probably in the envelopes. For the membranes 

 of the brain, see Brain and Spinal Marrow, 624. 



614. The Brain, Encephalon, 



is a mass consisting of nervous substance, which, surrounded by 

 three concentric membranes, fills up the cranial cavity, and con- 

 tains, in its interior, four spaces connected together. Its surface is 

 covered by a gray (cortical) substance, from one to one and a half 

 lines thick, the (medullary) substance lying under that is white. 



