368 
PLINY'S KATTJRAL HISTOET. 
[Book IX. 
sees that it is even exhaled*^ from them ? and when we find, 
too, that it can even enter the very depths of the earth, an 
element of so much greater density, a thing that is proved by 
the case of animals which always live under ground, the mole 
for instance ? There are other weighty reasons as well, which 
induce me to be of opinion that all aquatic animals respire, 
conformably to their natural organization ; for, in the first place, 
there has been often remarked in fishes a certain degree of an- 
helation during the heat of summer, and at other times again, 
a kind of leisurely gaping,*^ as it were. And then, besides, we 
have the admission of those who are of the contrary opinion, 
that fishes do sleep ; but what possibility is there of sleeping*^ 
wdthout respiring as well ? And again, we see their breath 
disengaged in bubbles which rise to the water's surface, and 
the influence too of the moon makes even the very shells 
grow in bulk. 
Eut the most convincing reason of all is, the undoubted fact 
that fishes have the power of hearing and of smelling, two 
senses for the operation of both of which the air is a necessary 
vehicle ; for by smell we understand nothing else than the air 
being charged with certain particles.^^ However, let every 
person form his own opinion on these subjects, just in such way 
as he may think best. 
E'either the balsena nor the dolphin has any gills.^^ Eoth 
43 In the shape of vapour raised by the action of the sun. In accord- 
ance with this opinion, Cicero says, De Nat. Deor. B. ii. s. 27, " The air 
arises from the respiration of the waters, and must be looked upon as a 
sort of vapour coming from them." 
But, as Hardouin remarks, this act on the part of the fish is caused 
as much by the water as the air. 
As Hardouin remarks, this is a somewhat singular notion that sleep 
is produced by the action of the lungs. 
46 Hardouin asks, what this has to do with the question about the air 
which Pliny is here discussing ? and then suggests that his meaning may 
possibly be, that the moon has an influence on bodies through the medium 
of the air, in accordance with the notion of the ancients that the respira- 
tion was more free during the time of full moon. Littre says, that Pliny's 
meaning is, that since the influence of the moon is able to penetrate the 
waters, the air and the vital breath can of course penetrate them also. 
47 See B. X. c. 89, where this subject is further discussed. 
48 " Infectum aera." 
49 See Aristotle, De Part. Anim. B. iv. c. 13, and Hist. Anim. B. viii. 
c. 2. 
