THE UNCONSCIOUS ACTION OF THE BRAIN. 55 l 



We next pass to a set of centres somewhat higher, those which form 

 the summit, as it were, of this spinal cord, which are really embedded 

 in the brain, but which do not form a part of that higher organ, which 

 is in fact the organ of the higher part of our mental nature, yet which 

 are commonly included in that which we designate the brain. In fact, 

 the anatomist who only studies the human brain is very liable to be 

 misled in regard to the character of these different parts, by the fact 

 that the higher part that which we call the Cerebrum is so immensely 

 developed in Man, in proportion to the rest of the animal creation, that 

 it envelops, as it were, the portion of which I am about to speak, con- 

 cealing it, and reducing it apparently to the condition of a very subor- 

 dinate part; and yet that subordinate part is, as I shall show you, the 

 foundation or basis of the higher portion the Cerebrum itself. The 

 brain of a Fish consists of very little else than a series of these ganglia, 

 these little knots the word " ganglion " means " knot," and the gan- 

 glia in many instances, when separated, are little knots, as it were, upon 

 the nerves. The brain of a fish consists of a series of these ganglia, 

 one pair belonging to each principal organ of sense. Thus we have in 

 front the ganglia of smell, then the ganglia of sight, the ganglia of 

 hearing, and ganglia of genei*al sensation. These constitute almost 

 entirely the brain of the fish. There is scarcely any thing in the brain 

 of the fish which answers to the Cerebrum or higher part of the brain 

 of man. I will give you an idea of the relative development of these 

 parts. [Dr. Carpenter made other sketches on the black-board, to rep- 

 resent these ganglia of sense in man and the lower animals.] Now, the 

 Cerebrum in most fishes is a mere little film, overlying the sensory tract, 

 but in the higher fish we have it larger ; in the reptiles we have it 

 larger still ; and in birds we have it still larger ; in the lower mammalia 

 it is larger still ; and then as we ascend to man this part becomes 

 so large in proportion that my board will not take it in. This Cere- 

 brum, this great mass of the brain, at the bottom of which these 

 Ganglia of Sense are buried, as it were, so overlies and conceals them 

 that their essential functions for a long time remained unknown. 

 Now, in the Cerebrum, the position of the active portion, what we call 

 the ganglionic matter, that which gives activity and power to these 

 nervous centres, is peculiar. In all ganglia this " gray " matter, as it 

 is called, is distinct from the white matter. In ordinary ganglia, this 

 gray matter lies in the interior as a sort of little kernel ; but in the 

 Cerebrum it is spread out over the surface, and forms a film or layer. 

 If any of you have the curiosity to see what it is like, you have only to 

 get a sheep's brain and examine it, and you will see this film of a red- 

 dish substance covering the surface of the Cerebrum. In the higher 

 animals, and in man, this film is deeply folded upon itself, with the 

 effect of giving it a very much more extended surface, and in this man- 

 ner the blood-vessels come into relation with it ; and it is by the changes 

 which take place between this nervous matter and the blood that all 



