FUNCTIONS OF THE BRAIN. 395 



3. Functions of the Brain. 



PHYSIOLOGISTS have in all ages sought for an elucidation 

 of the functions of the brain by the accurate examination of 

 its structure, which evidently consists of a congeries of me- 

 dullary fibres, arranged in the most intricate manner. Great 

 pains have been bestowed in unravelling the tissue of these 

 fibres, in the hope of discovering some clew to the perplex- 

 ing labyrinth of its organization: but nearly all that has been 

 learned from the laborious inquiry, is that the fibres of the 

 brain are continuous with those which compose the columns 

 of the spinal marrow; that they pass^ in their course, through 

 masses of nervous matter, which appear to be analogous to 

 ganglia; and that their remote extremities extend to the sur- 

 face of the convolutions of the brain and cerebellum, which 

 are composed of a softer and more transparent gray matter, 

 termed the cortical or cineritious substance of the brain. 



It is a remarkable fact, that in vertebrated animals all the 

 organs which are subservient to the sensorial functions are 

 double, those on one side being exactly similar to those on 

 the other. We see this in the eyes, the ears, the limbs, and 

 all the other instruments of voluntary motion; and in like 

 manner the parts of the nervous system which are connect- 

 ed with these functions are all double, and arranged sym- 

 metrically on the two sides of the body. The same law of 

 symmetry extends to the brain: every part of that organ 

 which is found on one side is repeated on the other; so that, 

 strictly speaking, we have two brains, as well as two optic 

 nerves and two eyes. But in order that the two sets of 

 fibres may co-operate, and constitute a single organ of sen- 

 sation, corresponding with our consciousness of individual- 

 ity, it was necessary that a free communication should be 



compose the face : but the fallacy of this criterion of animal sagacity has been 

 shown in a great many cases. 



