expels particles rendered effete, and these are supplied by
others from without, during inspiration; and this alter-
nation continues so long as life endures." It emanates
from an early stage of physiology, no doubt, but yet it
does clearly intimate that without such an alternation life
could not be maintained—that a renewing power from
without, and an expulsion of something prejudicial from
within, are necessary to animal existence. Democritus
(of Abdera), Anaxagoras and Diogenes are cited by Aris-
totle[1] as believing respiration to be necessary for all crea-
tures (in opposition to himself, who limited the process to
air-breathing animals), and he has given their account of
the process in fishes and oysters (molluscs). " Anaxagoras
says that fishes, during respiration, discharge the water
through the branchiæ, and that then, as there may not be
a vacuum, they draw in air which is in the mouth; and
Diogenes maintains that, when fishes discharge the water
through the branchiæ, they draw in, by means of the void
created in the mouth, the air which is ever present in
water and encircling the mouth." Democritus advanced
a step nearer to modern teaching, in accounting for fishes
dying when out of the water by their then taking in too much air; as, when in the water, they can take in only
a moderate quantity." But all this was objected to, abso-
lutely, by Aristotle, both because of his own more restricted
views of respiration, and of the apparent discrepance of
the theories with common sense, and thus was he led, in
- ↑ De Respirat. 2. i.
