128 Dr. Frederick Waller Mott [April 21, 



activities occurring in the cell bodies of the nervous units, but we 

 know very little or nothing of the biochemical processes occurring in 

 the neurones when we think, and feel, and move, and have our being. 

 Some authorities presume to know the biophysical processes which 

 take place, and I shall speak of these later on. One fact we do 

 know, is, that if blood for a few seconds fails to reach the mantle of 

 grey matter which covers the surface of the brain, there is loss of 

 consciousness, as in fainting. Consciousness then depends upon the 

 vital functions of these nervous elements in the grey rind or cortex 

 of the brain. The physiologist Flourens taught that all parts of 

 this grey substance were of equal value as regards function. This 

 doctrine, however, was even worse than that of phrenology which it 

 was directed against. The grey cortex or rind in the human brain 

 is, as you observe, thrown into a number of folds by fissures (Fig. 4). 

 These folds on the brain's surface become more numerous and com- 

 plex the higher we rise in the zoological scale, until in a cultured 

 European it finds its greatest development. Anatomically speaking, 

 this increasing number of folds means an increase in number of the 

 nervous units of the grey matter without an inconvenient increase in 

 the size of the head. I hold up to you the brains of an idiot and a 

 chimpanzee, you will observe there is not much difference. It has 

 been shown that the intellectual faculties are more developed in 

 persons with complex convolutions, and this means increased numbers 

 of nervous units in the grey matter, especially in certain regions 

 which I shall indicate to you later. With the death and disappear- 

 ance of these nervous units paralysis of mind and body ensues. 



Intellectual processes depend not so much upon relative increase 

 of brain weight as increase of the superficial area of the mantle of 

 nerve cells of certain regions. How has it been ascertained that 

 certain portions of the brain have definite functions? The first step 

 in this direction was the observation that persons who suffered with 

 injury or disease of the left half of the brain were not only liable 

 to paralysis of the right half of the body, but also to loss of speech. 

 Subsequently Broca determined the exact portion of the brain which 

 is connected with the function of articulate speech. Later it was 

 shown that destruction of a certain region produced word deafness ; 

 a person would not understand the meaning of words although he 

 could hear sounds. Further back still, there is a portion of brain 

 which, if destroyed, is followed by word blindness, a person so 

 affected would be able to converse, but would not be able to read 

 aloud, although he is not blind. It is only written language which 

 has no meaning to him. It is probable, therefore, that all right- 

 handed people use the left half of the brain much more than the 

 right. The whole of the central portion of the brain has been found 

 by experiments on animals, and by applying that knowledge to 

 diseases in man, to be tactile-motor in function — that is to say, it is 

 the part of the brain by which voluntary movements are directed and 

 controlled ; it is also the part of the brain where sensations coming 



