‘ 
350 Morton’s Crania Americana. 
great power of smell, to 120 square inches. The optic nerve in 
the mole isa slender thread, and its vision is feeble ; the same nerve 
is large and thick in the eagle, accompanied by intense powers of 
sight. Again, the fact admits of detuoustration, that deficiency 
in the size of the brain is one, although not the only, canse of 
idiotey. Although the brain be healthy, if the horizontal circum- 
ference of the head, with the muscular integuments, do not ex- 
ceed thirteen or fourteen inches, idiotcy is the zvariable conse- 
quence. Dr. Voisin states that he made observations on the 
idiots under his care at the Parisian Hospital of Incurables, and 
found that in the lowest class ef idiots, where the intellectual 
manifestations were null, the horizontal circumference, taken a 
little higher than the orbit, varied from eleven to thirteen inches, 
while the distance from the root of the nose backwards, over the 
top of the head, to the occipital spine, was ouly between eight 
and nine inches; and he found no exception to this fact. “If, 
therefore, extreme defect of size in the brain be invariably accom- 
panied by mental imbecility, it is a legitimate inference that size 
will influence the power of manifestation through all other gra- 
dations of magnitude, always assuming other conditions to be 
equal. 
Physiological authorities are equally explicit on this subject. 
Magendie says, “the volume of the brain is generally in direct 
proportion to the capacity of the mind. We ought not to suppose, 
however, that every man having a large head is necessarily a pet- 
son of superior intelligence ; Sa there are many causes of ali ang- 
mentation of the volume of the head besides the size of the brain; 
but it is rarely found that a man distinguished by his mental fac- 
ulties has not a large head. The only way of estimating the vol- 
ume of the brain, in a living person, is to measure the dimensions 
of the skull; every other means, even that proposed by Camper, 
is uncertain.””. 
e difference of mental power-between young and adult 
minds, is a matter of common observation. The difference in 
the weights of their brains is equally decided. 
According to Cruveilhier, in three young subjects, the weights 
of. the brains were as follows: 
In the first, the brain weighed 2 lbs. 2 oz. ; the cerebellum, 
A$ 02. ; together, 2 Ibs. 64 0z. In the second, the brain weighed 
2 Ibs. 8 oz. ; the cerebellum, 34 02. ; together, 2 lbs. 114 02. in 
