GENERAL ÏCHARACTERISŒICS «
23
'
above them and controls itsown life—processe‘son a higher,
leVel.
_
'
'
'
'
Apart from_the temperature,
that is, the quantity of watef’ it'contains 1nadd1tmn to
and
regulatedma1nlyfromWit-hin
n0t _-from without.
Thus, it has
that the
blood—pressure, though
to 8 to 10attnospheres, ,
is .far below the pressureof the
in the Cartilaginous shes, where a
prevails. This‘_=blood-pféssure is much the saifenas that,
found in
and
higher vertebrates
depends upon the power
by living membranes
of selectirig; and excluding the varioàingredients,
or otherwise, in the water.
_
_
=
'
,
}
,
Theprocesses of life,metabolic changes, that
within
.
,
"the
are-thus distinct from
surrounding pr0cesSes. _
-,
»
,Eaç‘hgsh:isïà_li—ttle wod
World.
à:;
takes -in_has
the
suit its needs
thesamewayas
VertebrateS,_ but the details; ofeect1gth13
*dîgçsti9nfd jf@ôd" proceeds,
‘
alengthesamehnæbutthe
Œ£dl‘fs ifor. dis—;
,
f elementaryœndüwnTheheartwnhsmoorthree
,.
€harbers, ‘fhÔugh agreatadvanœ@nanythmgseenænong
the invertebrates, makes little iornodist1nctionbeüveen Ï
venous
and oxygenated blood, Thé” purication
'
Of the
latter takes place in the gills after it has passed through the
'
heart, and it is only in the lung-breathig shes and those
With an additional breatbing organ—apart frôi’the gills—
_
that the head and brains receive a purer supply thanthete3t
'
Ï
—o£_the body. The brain power and psychiçlife of shes,
}
as of higher
'
'fï°iï of Oxygen by
£î{c.Ï …:
higher
Theorganfor theexcreOnofwagœ
.…
liquid products; the1dneyslsatamuchlowerstageof