THE SENSORIAL FUNCTION. 1 19 



dog had been the subject, it would have been very considerably larger, compar- 

 ing the general bulk of each animal. This is singular. The human brain 

 largest in comparative bulk; then the brain of the dog, the horse, the ox. Thus, 

 would they be classed in the scale of intelligence. 



If the brain is more closely examined, it will be found that there is none of 

 the roundness and the broadness of that in the human being; it is comparatively 

 tame and flat. There is some irregularity of surface, some small projections and 

 depressions ; but they, too, are comparatively diminutive and inexpressive. Were 

 the brain of the beaver, of the hare, or the rabbit, or of almost any bird, sub- 

 stituted for it, there would be no convolutions or irregularities at all. 



These irregularities are not so bold and so deep in the ox as in the horse, nor 

 in the horse as in the dog. We do not know enough of the functions of any 

 part of the brain to associate these convolutions with any particular powers of 

 mind, or good or bad propensities, although some persons, who are wise above that 

 which is written, have pretended to do so. It would occupy too great a por- 

 tion of this volume to enter into these questions; but there are some diseases 

 to which the horse is subject, and a very useful operation — the division of 

 some of the nerves for certain purposes, and which could not be understood with- 

 out a previous slight account of this important organ. 



When the brain is cut, it is found to be composed of two substances very 

 unlike in appearance (m, p. Ill) ; one, principally on the outside, grey, or ash- 

 coloured, and therefore called the cortical (bark-like) from its situation, and 

 eineritious (ashen) from its colour ; and the other, lying deeper in the brain, 

 and from its pulpy nature called the medullary substance. Although placed in 

 apposition with each other, and seemingly mingling, they never run into the 

 same mass, or change by degrees into one another, but are essentially distinct in 

 construction as well as in function. 



The medullary portion is connected with the nervous system. The nerves 

 are prolongations of it, and are concerned in the discharge of all the offices of 

 life. They give motion and energy to the limbs, the heart, the lungs, the 

 stomach, and every part connected with life. They are the medium through 

 which sensation is conveyed ; and they supply the mind with materials to think 

 and work upon. 



The eineritious part has a different appearance, and is differently constituted. 

 Some have supposed, and with much appearance of truth, that it is the residence 

 of the mind — receiving the impressions that are conveyed to the brain by the 

 sensitive nerves, and directing the operation and action of those which give 

 motion to the limbs. In accordance with this, it happens that, where superior 

 intelligence is found, the eineritious portion prevails, and where little beside brute 

 strength and animal appetite exist, the medullary portion is enlarged. There 

 is, comparing bulk with bulk, less of the medullary substance in the horse than 

 in the ox, and in the dog than in the horse. The additional bulk of brain is 

 composed of eineritious matter ; and how different is the character of these 

 animals ? — the sluggish, stupid ox, and the intelligent horse ; the silly sheep, 

 and the intellectual companionable dog ! 



In a work like this, it would be somewhat out of place to enter deeply into 

 any metaphysical speculation ; but the connexion between the eineritious part 

 of the brain and the intellectual principle, and that between the medullary 

 portion and the mere animal principle, do seem highly probable. The latter 

 is the medium through which the impression is conveyed, or the motion is 

 effected ; the former is the substance to which that impression is referred — 

 where it is received, registered, and compared, and by which the operation of 

 the motor nerves is influenced and governed. 

 The cortical substance is small in the quadruped ; for io their wild state 



