Structure and Qeconomy of Whales. 423 
1 his conftrudlion of parts anfwers a purpofe limilar to that 
of the epiglottis in the quadruped ; it may be confidered as the 
epiglottis and the arytenoid cartilages joining, to make a 
tubular or cylindrical epiglottis, inftead of a valvular one. 
The reafons why there fhould be fo peculiar a conftrudtion of 
parts do not at firft appear ; but we certainly fee by it an 
ablolute guard placed upon the lungs, that no water fhould get 
into them. 
This tribe being without the projecting tongue of the qua- 
druped, and wanting its extenfive motion, and the power 
of lucking things into the mouth, may probably require 
the conftrudtion between the air and lungs to be more perfect ; 
but how far it is fo, I will not pretend to fay. 
The lize of the Brain differs much in different genera of this 
tribe, and likewife in the proportion it bears to the bulk of 
the animal. In the Porpoife, I believe, it is largeff, and 
perhaps in that refpedt comes neareft to the human. 
The lize of the cerebellum in proportion to that of the cere- 
brum is fmaller in the human fubjedt than in any- animal with 
which I am acquainted. In many quadrupeds, as the Horfe, 
Cow, &c. the difproportion in lize between cerebellum and 
cerebrum is not great, and in this tribe it is ffill lefs ; yet not 
fo fmall as in the bird, &c. 
The whole brain in this tribe is compadt, the anterior 
part of the cerebrum not projecting fo far forwards as in either 
the quadruped or in the human lubjedt ; neither is the medulla 
oblongata fo prominent, but flat, lying in a kind of hollow 
made by the two lobes of the cerebellum. 
The brain is compofed of cortical and medullary fubftances, 
very diftindtly marked ; the cortical being, in colour, like the 
tubular fubftance of a kidney; the medullary, very white. 
Vo l. LXXVII. O o o Thefe 
