oS CAVITIES OF HEART 67 
has remained. This fact, therefore, shows that the mammal 
cannot have been derived from a bird-like ancestor, but that 
m 
of ec Fic. 43.—Lepus cuniculus. Veu- 
7 tral view of the vascular sys- 
tem. The heart is somewhat 
displaced towards the left of 
the subject; the arteries of 
the right and the veins of the 
left side are in great measure 
removed. a.epg, internal mam- 
mary artery ; a./, anterior facial 
vein ; a.m, anterior mesenteric 
artery ; a.ph, anterior phrenic 
vein ; az.v, azygos vein ; br, 
brachial artery ; c.7/.a, common 
iliac artery; c.i/.v, common 
iliac vein ; cw, coeliac artery ; 
d.ao, dorsal aorta: e.c, external 
carotid artery ; ¢.i/,a, external 
iliac artery ; ¢.il.v, external 
iliac vein ; e.ju, external jugu- 
lar vein ; /m.a, femoral artery ; 
Jm.v, femoral vein ; /.v, hepatic 
veins ; 7c, internal’ carotid 
artery ; ¢.cs, intercostal vessels ; 
i.dl.d, internaliliac artery ; 7.7/.7, 
internal iliac vein ; 7.jv, internal 
jugular vein; 7./, iliolumbar 
artery and vein ; 7, innomin- 
ate artery ; d.au, left auricle ; 
Z.c.c, left common carotid ar- 
tery ; l.pr.c, left pre-caval vein ; 
dv, left ventricle ; m.sc, median 
sacral artery ; p.a@, pulmonary 
artery ; p.epg, epigastric artery 
and vein; p.f, posterior facial 
Jes vein; p.m, posterior mesen- 
spm teric artery; p.ph, posterior 
m.se phrenic veins ; pt.c, post-caval 
vein ; p.v, pulmonary vein ; 7, 
THE renal artery and vein; 7.av, 
right auricle ; 7.c.c, right com- 
——c.il.a mon carotid artery ; 7.pre, right 
Zila etla pre-caval vein ; 7.v, right ven- 
ul tricle ; s.cl.a, right subclavian 
Tl ePGg: artery; s.cl.v, subclavian vein ; 
Jma spm, spermatic artery; s.vs, 
4 vesical artery; w/, uterine artery 
and vein ; vr, vertebral artery. 
(From Parker’s Zootomy.) 
both must have independently come from an ancestor with 
both halves of the aortic arch present, of which one half 
has disappeared in one group, and the other half in the 
other. It is an interesting fact, too, to notice that the four 
