THE BRAIN. 545 
as well as its quality can be increased by use, seems to have 
been established by the measurements, at different periods of 
‘development, of the heads of those engaged in intellectual pur- 
suits, and comparing the results with those obtained by similar 
measurement of the heads of those not thus specially employed. 
Of course, it must be assumed that the head measurement is a 
gauge of the size of the brain, which is approximately true, if 
Fig. 396. Fie, 397, 
Fig. 396.—Brain of cat, seen from above (after Tiedemann). 
Fic. 397.—Brain of dog, seen from above (after Tiedemann). 
not entirely so. There are many facts which go to show that 
the habits of ancestors tend to become almost the instincts of 
posterity, even in the case of man. It has been noticed that a 
facility in the acquisition of scholarship (languages, literature) 
has, in many cases, been associated with scholarly habits in 
numerous generations of ancestors. The inheritance of mental 
traits, which can not be considered wholly apart from a physi- 
cal basis in the nervous system, and especially in the cerebrum, 
is a subject of great interest, but too wide for more than a pass- 
ing allusion here. 
Recent investigations seem to show that the development 
of the ganglion cells of the brain takes place first in the me- 
dulla, next in the cerebellum, after that in the mid-brain, and 
finally in the cerebral cortex. Animals most helpless at birth 
are those with the least development of such cells. The me- 
dulla may be regarded in some sense as the oldest (phylogeneti- 
cally) part of the brain. In it are lodged those cells (centers) 
which are required for the maintenance of the functions essen- 
tial to somatic life. This may serve to explain how it is that 
so many centers are there crowded together. It is remarkable 
that so small a part of the brain should preside over many im- 
portant functions; but the principle of concentration with pro- 
gressive development, and the law of habit making automatism 
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