28 THE HUMAN BRAIN. 



and to the great blood-vessels ; and also fibres pass to communicate 

 with the capital nervous system. 



From the general tenor of these two systems it appears that the 

 cerebral is the engine and representative of the mind, and of the 

 body as constituted in the hierarchy of the mind, while the sym- 

 pathetic system is the nervous engine and representative of the body 

 considered independently, as possessing a life or mind in itself so 

 far as this system can arouse it. Consciousness does not here come 

 in question. Many of our impressions are unconscious, nay perhaps 

 all through the longer part of their course, though travelling along 

 the cerebral lines. And again, the bodily organs, as the liver or 

 the kidneys, require to exercise processes of selection, and acts of 

 composition and elimination, to which nothing less than a stupen- 

 dous bodily judgment is adequate. Mental judgment would not be 

 fine enough for the work; and it is only mental judgment and 

 faculty which are conscious. 



The brain and its parts, including the spinal marrow, are clothed 

 with three membranes or skins. That next the brain is the pia 

 mater, which not only encloses the brain, but dips down into its 

 folds, and probably ramifies more and more finely through its minute 

 divisions, acting as a framework to the nervous substance : it is full 

 of delicate vessels which supply the brain with blood. The next 

 membrane is the arachnoid, which is said to form a shut bag like a 

 double nightcap, in the inside of which a lubricating fluid is given 

 out, the whole constituting a kind of " water bed"* on which the 

 brain may undulate. The next membrane is the dura mater, lining 

 the movable arachnoid on the side towards the brain, and lining the 

 bony skull on the other side, and being separable into two layers to 

 suit these two situations or offices. It is the strongest of the mem- 

 branes of the brain, and gives off membranous pipes which receive 

 and envelop the nerves at their exit from the skull and spine : it also 

 sends down tight sheets or processes between the two halves of the 

 cerebrum, and between the cerebrum and cerebellum, whereby it 



* Water beds of this kind, i. c, serous membranes, are prepared for all the 

 viscera; and bursse or water cushions are frequently apposed in the joints; 

 where these are met with they are the means and evidences of some motion 

 performed. 



