308 
(h) alone has a separate origin. The common 
carotid in the Kangaroo gives off the thyroid 
artery, and afterwards divides opposite the 
transverse process of the atlas into the external 
and internal carotids. The internal carotid 
describes a sharp curve at its origin, and passes 
along the groove between the occipital condyle 
and the exoccipital process to the foramen ca- 
roticum. The vertebral arteries are given off 
by the subclavians, and to the skull, as 
usual, through the vertebral foramina of the 
cervical transverse processes. They unite be- 
neath the medulla oblongata to form the basilar 
artery, which sends off at right angles to the 
cerebellum two branches as large as itself: it 
divides opposite the anterior margin of the 
pons Varolii, and the diverging branches are 
connected by two straight transverse canals, 
before they anastomose with the internal caro- 
tids to form the circle of Willis. No pecu- 
liarly marsupial condition occurs in the distri- 
bution of the other arteries of the head, or 
those of the neck, the chest, and anterior ex- 
tremities; but I may observe that in the Koala, 
Wombat, Kangaroos, Potoroos, most Phalan- 
gers, ( Phal. Cookii is an exception,) most Pe- 
taurists, ( Pet. Sciureus is an exception,) the 
Opossums, Bandicoots, and Phascogales, the 
brachial artery perforates the internal condyle 
of the humerus; it passes over that condyle, 
impressing it with a more or less deep groove 
in the Dasyures and Thylacine. 
In the abdomen, the primary branches of 
the aorta are sent off in the same order as in 
most of the ordinary Mammalia, with the ex- 
ception of the constant absence of an inferior 
mesenteric artery. This modification probably 
relates to the simplicity of the mesenteric at- 
tachment of the intestines above described. A 
still more marked example of the oviparous 
affinities of the Marsupialia, as exemplified in 
the arterial system, occurs in the mode of 
origin of the great arteries of the posterior 
extremities. In Man and the ordinary Mam- 
miulia these are derived, as is well known, from 
a single trunk on each side—the common iliac 
artery; in Birds from two primary branches of 
the aorta, one corresponding with the external 
iliac and femoral, the other with the internal 
iliac and ischiadic arteries. In the Kangaroo 
and Phalangista vulpina the aorta gives off, 
opposite the interspace of the two last lumbar 
vertebra, the iliac arteries ; but these are after- 
wards resolved into the ordinary branches of the 
external iliac of the placental Mammalia, with 
the addition of the ilio-lumbar artery. The 
trunk of the aorta, much diminished in size, 
maintains its usual course for a very short 
distance, and then gives off the two internal 
iliacs, and is continued as the ¢ arteria sacra 
media’ to the tail. The transitional cha- 
racter of this part of the marsupial sangui- 
ferous system between the oviparous and pla- 
cental types, is manifested in the large size of 
the external iliacs as compared with the internal 
iliaes, their greater share im the supply of blood 
to the hinder extremities, and the brevity of 
the aortic trunk between their origins. In 
most Birds the femorals or external iliacs are 
MARSUPIALIA. 
smaller than the ischiadic or internal iliac 
arteries subsequently given off. At the uppel 
part of the thigh the femoral divides into 
two equal branches; the one which corresponds 
with the radial artery in the fore leg (m, fig.134) 
principally supplies the foot in the Kangaroos 
it passes along the back of the radius, be! 
the gastrocnemius internus and tibialis posticu 
and divides a little above the internal malleolus. 
The smaller division (/, fig. 134), which folle 
the ordinary course of the femoral along the pe 
teal space, is lost upon the inner and ior F 
of the tarsus; the larger branch winds over th 
malleolus to the front of the tarsus, sends off 
the anterior tarsal artery, and is then continued 
along the inner and afterwards the under part of 
the metatarsal bone of the long-and strong toe. 
In fig.134, a is the trunk of the celiac artery 
b that of the superior and inferior mesenteri 
arteries; c is the capsular artery of the left side; 
d, d, the renal arteries; e the s tic artery, 
of which the left branch is shown continued to 
the left ovarium g, which, with the uterus 
vagina s, and bladder ¢, is drawn to the rightside; 
the spermatic arteries = — but 
separately in the male Vulpine cary i 
the diavel iliac, coreisnatiel with ré ! 
mon iliac in placental Mammalia, and wit 
the femoral artery in Birds, (see Vol. i. pe 33) 
Sigs. 170, 23 ;) below these are given off A, t 
arteries corresponding with the ischiadie ar. 
teries in Birds, (Vol. i. p: 337, fg. 170, 26,) 
and with the internal iliacs in nalia; 
[they are represented of too small a size in 
the cut]; & is the femoral artery; / the ex- 
ternal, m the internal branch; é is the saere 
median or caudal artery, which is protecte 
in its course along the tail by the hem. 
apophysial or chevron-like processes of the 
caudal vertebre. This artery of course cor- 
responds in size with the developement ane 
functional importance of the tail, and must b 
DOS | 
Es 
E 
' 
ya 
rudimentary in the tail-less or nearly tail-les; 
Marsupials, such as the Cheropus, Koala, an 
Wombat. . 
With respect to the veins of the Marsupi 
it may here be noticed that the iliac vei 
combine to form the trunk of the abdomin 
cava, as in the rest of the Mammalia, witho 
conveying any part of their blood to the kit 
neys: in the Kangaroo they both pass on 
central aspect of the iliac arteries. The re 
veins, in like manner, directly communie 
with the abdominal cava, and do not cont 
bute any share in the formation of the por 
vein. This great secerning trunk of the hepa 
organ presents the strictly mammalian con 
tion, being formed by the reunion of the gast 
intestinal, pancreatic, and splenic veins. Ti 
in the chest that we first meet with decie 
traces of the oviparous type of structure in 
venous system of the Marsupialia. The prim 
tive veins of the animal system of orga 
commonly called ‘ azygos,’ retain their orig git 
separation and symmetry; the left ‘ azyg 
bends over the left bronchus to com 
with the left anterior cava, and the rig 
gos over the right bronchus to join the rigi 
anterior cava. ‘The left anterior cava commol 
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