OF FISHES IN GENERAL. 
Z* 
No philofopher feems yet to have made obfervations 
fufficiently accurate, fully to determine this matter ; for 
is not yet afcertained, whether the neck of the canal 
be fupplied with a valve to emit air fecreted from the 
blood, or to receive it from the ftomach, or with a 
muffle that may equally ferve to admit, or eject it : And 
what militates againft Needham's opinion, is, that the 
cartilaginous fillies, which have nothing of this kind to 
aid their digeftive powers, are as remarkable for voracity 
as any other kind. 
The other ufe to which naturalifts have deftined this 
01 gan is, to lerve as a receptacle for air, inflead of the 
lungs in terreftrial animals, by which the neceffities of 
thefe creatures may be fupplied. The air bladder of 
fiihes is confined in a triangular fpace at the upper part 
o. the abdomen, and confifts of one, two, and fometimes 
three divifions, all feparated from the reft of the vifcera 
by a thin membrane, attached, on each fide, to the ribs; 
An apparatus of this kind, though we be not able to 
explain its ule, no one C3n imagine was formed in vain. 
It ts poffibie, that it may ferve fome purpofe different 
;rom any of the above, and probably more than one 
even of thefe. 
. Fliiles thus fitted for motion in their element, by their 
internal ftrufture, as well as by their outward lliape, and 
fitua.ion ol their fins, feem as well furnilhcd with 
e means of happinefs, as either quadrupeds or birds. 
" '■bdc they are furuifhed with an external covering, 
° e . tend them from injuries in the turbulent fluid which 
^ P ' ri ' ' u ' I hat fiimy and glutinous tubftance, which is 
^ ^ n oni the pores of all fidies, not only defends 
r bodies from accident, but is happily contrived to 
ter ® 0 bhruai° n to their progiefs through the wa- 
l * eudes tins fubftance, which defends ftieir bodies 
B 2 from 
