Strudlure and Oeconomy of Whales. 42$ 
oft from the medulla fpinalis are more uniform in fize than in 
the quadruped, there being no fuch inequality of parts, nor 
any extremities to be fupplied, except the fins. 
The medulla fpinalis is more fibrous in its ftruCture than in 
other animals ; and when an attempt is made to break it longi- 
tudinally, it tears with a fibrous appearance, but tranfverfely 
it breaks irregularly. 
The dura mater lines the fkull, and forms in fome the three 
proceffes anfwerable to the divifions of the brain, as in the hu- 
man fubjeCt ; but in others, this is bone. Where it covers the 
medulla fpinalis, it differs from all the quadrupeds I am ac- 
quainted with, inclofing the medulla clofely, and the nerves 
immediately palling out through it at the lower part, as they 
do at the upper, fo that the cauda equina, as it forms, is on 
the outfide of the dura mater. 
As the Organs of Senfe are varioufly formed in different ani- 
mals, fitted for the various modes of impreffion ; and as the 
modes are either increafed or varied, according to circumftances 
which make no part of the fenfe itfelf, but which are necel- 
fary for the oeconomy of the animal, we find the lenfes in this 
tribe varied in their conftruCtion, and in fome a fenfe is even 
wholly wanting. 
The organs of fenfe, which appear to be adapted to every 
mode of life, are thofe of touch and taffe ; but thole of lmell, 
fight, and hearing, probably require to be varied according to 
circumftances. Thus fmell may be increafed by a mode of 
impregnation, hearing by the vibration of different mediums, 
and fight by the different powers of refraction of different me- 
diums ; therefore, as animals are intended by nature to be dif- 
ferently circumftanced, fo are the fenfes formed. 
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