against  the  theory  founded  upon  this.bypotheaisj
from  some  apparent  anomalies  which  occasioi^
aHy  present  themselves,  we  must,  I  think,  admit
that  it  affords  the  best  explanation  of  the.  phe?^
nomena  of  any  theory  yet  proposed^,  and  tfaat^
therefore,  it  is  probably  the.  true  one.  .  .  n  -
The  maintenance  of  a  very  elevated  tempe?
rature  appears  to  require  the  concim^ce  of:  tmo
conditions;  namely,  first,  that  the  whole  of:  thB
blood.should  be  subjected  to  the  influ^ica  of  the
air,  and,  secondly,  that ;  that  air  should  be  pie^
sented  to  it  in  a  gaseous  state.  These,  then,  afe
the  circumstances  which  establish  the  great  idhr
tinction  between  warm.and  cold-blooded  animak;
a  distinction  which  at  once  stamps  the  character
of  their  whole  constitution.  It  is  the  condilMii
of  a  high  temperature  ia  the  blood  which  iraiseB
the  Quadruped  and  the  Bird  to  a  rank^  in  the
scale  of  vitality,  so  far  above  that  of  the  Reptile :
it  is  this  which  places  an  insuperable .  boundiEuy
between  Mammalia  and  Fishes.  However  the
warm-blooded  Cetacea,  who  spend  their  lives
in  the  ocean,  may  be  found  to  approximate
in  their  outward  form,  and  in  their  external
instruments  of  motion,  to  the  other  inhabitants
of  the  deep,  they  are  still,  from  the  ccmformatkn
of  their  respiratory  organs,  dependent  on  another
element.  If  a  Seal,  a  Porpoise,  or  a  Delphin
were  confined,  but  for  a  short  time,  under,  the
surface  of  the  water,  it  would  perish  with  the


CHI'.MiCAL  EFFECTS  OV  RESPIRATION.  341

ne  certainty  as  any  other  of  the  mammalia,
placed  in  the  same  situation.  We  observe  them
continually  rising  to  the  surface  in  order  to
breathe,  under  every  circumstance  of  privation
or  of  danger ;  and  however  eagerly  they  may
pursue  their  prey,  however  closely  they  may  be
pressed  by  their  enemies,  a  more  urgent  want
compels  them,  from  time  to  time,  to  respire  air
at  the  surface  of  the  sea.  Were  it  not  for  this
imperious  necessity,  the  Whale,  whose  enormous
iniik  is  united  with  corresponding  strength  and
swiftness,  would  live  in  undisturbed  possession
of  the  widely  extended  domains  of  the  ocean,
might  view  without  dismay  whole  fleets  sent  out
Hgainst  him,  and  might  defy  all  the  eflbrts  that
man  could  practise  for  his  capture  or  destruction.
