154 PRESIDENTS ADDRESS—SECTION J. 
organism may profoundly affect the functioning of the cortex. 
This is seen in those diseases of the cortex which constitute what 
is called “ mental disease.” In chronic cases of this we find the 
nutrition of the whole body becoming involved, so that after a 
time the patient may be said to be “insane” from the crown of 
his head to the sole of his foot. Or, conversely, take the effect 
of disease or-loss of a small portion of the body, such as the 
thyroid gland. The result is great mental depression, passing 
into a complete dementia. And what is very remarkable is the 
fact that if such a patient eats the corresponding portion of an 
animal, say, of a sheep, for a length of time, there gradually 
returns a decided improvement in “the mental condition. It is 
evident, therefore, that to get the fullest mental results, atten- 
tion must be paid to seeing that the organism as a whole is 
functioning in the most perfect manner. As Herbert Spencer 
has remarked: “In consequence of specialities of inheritance, 
specialities of education, and specialities of mode of life, high 
mental manifestations of certain kinds may go along with weak- 
ness of body. But classing such cases as abnormal deviations 
from that constitutional balance which is needful for survival 
through future generations, and limiting our attention to cases 
where no monstrosity has been produced by undue forcing of 
the individuals or his ancestors, we shall, I think, trace a con- 
nection between abounding physical vigour and power of think- 
ing and feeling, as well as between sluggishness of constitution 
and comparative inertness, intellectual and emotional.” In con- 
sidering the question of mind as correlate with brain growth, 
the portion of the brain that will be chiefly interesting to study 
will be the cortex cerebri, or at least some structures that help 
to form it. 
The cerebral cortex is the last portion of the organism to be 
developed, and at birth all the different fibres have not been pro- 
duced or properly organised. The most matured portion at 
birth corresponds roughly to the middle third of three trans- 
verse divisions of the cortex, and is often referred to as the 
motor region, because stimulation of this area with a feeble 
current of electricity elicits definite muscular movements. This 
area is apparently the sphere of bodily sensibility, and in pro- 
portion toe its development and growth arises the psychical idea 
of the ego, or self-consciousness. By means of the connections 
between this portion of the cerebrum and the rest of the body 
we are enabled to form ideas of our own personality. The fact 
that this portion of the cortex is the first to become organised, 
emphasises the importance of our developing a self-consciousness 
as early as possible. In cases of commencing disease of this 
part, as often appears in general paralysis of the insane, there 
may be, owing to pathological irritation, an exaggerated idea of 
personality and grandiose delusions ; or, in another class of cases, 
