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POPULAR SCIENCE REVIEW. 
pendent on the delicacy and fitness of the arrangements quite 
as much as on the strength of the current which supplies them, 
so in the case of the mind the result is dependent on the distri- 
bution and balance of the faculties and inclinations, and on 
other circumstances, none of which are proved to have any con- 
nection with the mass of cerebral substance. Certain it is that, 
although there are probably mental characters peculiar to large 
and small brains respectively, the size of the skull is, as any 
observer may easily satisfy himself, no good guide to the mental 
endowments. 
EXPLANATION OF PLATE. 
Figures 1 to 5, adapted from various writers, illustrate the development 
of the Brain, i. ii. iii. are the primordial vesicles ; h is the 
cerebral hemisphere j c the cerebellum. 
Fig. 1. The cerebro-spinal canal nearly closed in a chick, after tw'enty- 
four hours’ hatching. 
„ 2. The embryo brain and spinal cord of a chick, after thirty-six 
hours’ hatching, 
„ 0. Human brain at a very early period, seen in profile. 
,, 4. A somewdiat later style of development, viewed from above, and 
the hemisphere vesicles laid open. 
„ 5. A considerably more advanced brain. The hemispheres have 
acquired their ultimate proportions, conceal the parts deiived 
from the first and second vesicle, and rest on the cerebellum, 
but are not yet convoluted on the surface, 
„ 0. Horizontal section of the fore part of the skull, through the 
right side of the forehead, half an inch above the orbital 
margin, a a a. The sawn edge of bone ; h. section of the 
frontal sinus. It may be mentioned that -in the fore part the 
sinus had considerable vertical depth, but that at the part 
farthest back on the roof of the orbit the depth is slight. 
