[ *97 } 
argument why they refide on fhore the greateft part 
of their time, and that is, that the flefli of thefe 
creatures is analogous to that of other land animals ; 
and therefore, by over-long maceration, added to the 
fatigue of their charing their prey, they would fuffer 
fuch a relaxation as would deftroy them. It is well 
known that animals, which have lain long under water, 
are reduced to a very lax and even putrid ftate ; and 
the phoca muft balk in the air on fhore ; for while the 
folids are at reft, they acquire their former degree of 
tenfion, and the vigour of the animal is reftored ; and 
while he has an uninterrupted placid refpiration, his 
blood is refrefhed by the new fupply of air, as I have 
explained it above, and he is rendered fit for his next 
cruife : for a&ion waftes the moft exalted fluids of the 
body, more or lefs, according to its duration and vio- 
lence; and the reftorative reft muft continue a longer 
or fhorter time, according to the quantity of the pre- 
vious fatigue. 
Let us now examine by what power thefe animals 
are capable of remaining longer under water than 
land animals. 
All thefe have the oval hole open, between the right 
and left auricles of the heart, and, in many, the ca- 
nalis arteriofus alfo: and while the phoca remains 
under water, which he may continue an hour or two 
more or lefs, his refpiration is flopped, and the blood, 
not finding the paflage through the pulmonary artery 
free, ruflies through the hole from the right to the left 
auricle, and partly through the arterial canal, being a 
fhort paflage to the aorta, and thence to every part of 
the body, maintaining the circulation : but, upon riling 
to 
