C ) 
Heat of ours would be a Fever in them, and Mortal, 
wherefore we need not wonder they ca:^not live in the 
Air ; for the Nitre of the pure Air is in too great a 
quantity, and too fubtile , fo that it diffolves their 
Blood too much, and niakes it too Fluid ; whereas the 
Nitre in the Water is more grofs and in lefler proporti- 
on, whence it gives their Blood only a Fluidity requi- 
fite to keep it in its natural State : To prove that 
it is in the Bronchi^e that this divifion is performed, 
we need but obferve their extraordinary redneft above 
any other part of the Body, a Proof that the Blood is 
there more divided : Fifti are found to dye in Wa- 
ter Frozen over, which happens plainly from their Com- 
munication with the outward Air, being hindred by 
the Ice. 
The Heart of Fifli is different from that of o- 
ther Animals in its having but One Ventricle for it 
has only the Fena Cava and the Aorta that open into 
it, having no Lungs fo that by the Aorta the Blood 
comes out of the Heart, which is branched into a 
Thoufand Capillaries over the Bronchia^, and is after 
re-united ; which re-union is made under the Bafis 
of the Cranium ; and becaufe the Blood , when 
once there, has no need of being forced higher up- 
wards, they have no occafion for a fecond Ven- 
tricle for that purpofe , as Terreftrial Animals 
have. 
The Re- union of theft Capillaries of the Bron- 
chias being made, they form Two large Trunks, of 
which one proceeds towards the Head, and the other 
towards the lower parts. 
Fi(h have a Diaphragm, but not for the fame pur- 
pofe as in other Animals that Breath ? it is always 
Strait and Tenfe, and Perpendicular on the Vertebrae, it 
hinders the fermenting Salts thac exhale from the Inte- 
R r r (tines 
