112 
ANATOMY AND PHYSIOLOGY 
The substance of the brain is more visibly fibrous than 
I ever saw it in any other animal, the fibres passing 
from the ventricles as from a centre to the circumference, 
which fibrous texture is also continued through the 
cortical substance. The nerves going out from the 
brain I believe are similar to those of the quadruped, 
except in those which want the olfactory nerves. The 
medulla spinalis is much smaller in proportion to the 
size of the body than in the human species, but still 
bears some proportion to the quantity of brain, for in 
the porpoise where the brain is largest, the medulla 
spinalis is largest, yet this did not hold good in the 
spermaceti whale , the size of the medulla spinalis appear- 
ing to be proportionally larger than the brain, which 
was small when compared to the size of the animal. It 
has a cortical part in the centre, and terminates about 
the twenty-fifth vertebra, beyond which is the cauda 
equina, the dura-mater going no lower. The nerves 
which go off from the medulla spinalis, are more uni- 
form in size than in the quadruped, there being no such 
inequality of parts, nor any extremities to be supplied 
except the fins. The medulla spinalis is more fibrous 
in its structure than in any other animal, and when an 
attempt is made to break it longitudinally, it tears with 
a fibrous appearance, but transversely it breaks irregu- 
larly. The dura-mater lines the skull, and forms in 
some the three processes, answerable to the division of 
the brain as in the human subject, but in others this is 
bone. Where it covers the medulla spinalis, it differs 
from all the quadrupeds I am acquainted with, enclosing 
