482 On the Nervous Systems. of 
animals, In the higher orders, the brain is larger 
in proportion to) the spinal marrow, and the 
spinal marrow is also larger in proportion to the 
nerves connected with it... The human brain is 
by. mich the largest in proportion to the rest of 
the nervous ‘system: Itcommonly weighs from 
two» to three pounds, ‘or }upwards; but very 
‘rarely reaches four pounds. In other. warm- 
blooded animals the brain diminishes #@m volume, 
in proportion as the spinal. marrow enlarges, 
and in some fishes the bulk of the two other 
parts of the brain scarcely surpasses that of the 
médulla oblongata, and this scarcely exceeds the 
spinal marrow. The intellectual powers of ani= 
mals.seém to correspond in’ extent with the pro- 
portion of the brain to the test .of the nervous. 
system, and: thé: perfection of its organization; 
Whilst. the acuteness of sensation and the force 
and) rapidity of voluntary motion appear to de-. 
pend upon the proportion of nerve, distributed. 
to the organs of sense and voluntary motion 
rather than on the proportion of brain. All 
animals, which are as large as man, have larger 
nerves,.and greater strength. The smaller ani- 
mals have much larger nerves in proportion to 
their limbs, . Fishes, which have very small 
brains, have very acute feeling and move with 
great rapidity and force. _ Many animals have 
more acute senses and greater. powers of motion 
