s equal,
and then greater, than the resistance at A, and the rush of blood, now
of a mixed quality passes through that aperture. It selects the dorsal
aorta, because the carotid arch, plugged by the carotid gland, offers
the greater resistance. Presently, however, the back resistance of the
filled dorsal aorta rises above this, and the last flow of blood, from the
ventricular systole-- almost purely oxygenated blood for the left
auricle-- goes on towards the head.

Section 9. At the carotid gland the carotid artery splits into -an- [a]
-external carotid- [lingual] (e.c.), and a deeper internal carotid. The
dorsal aorta passes round on each side of the oesophagus, as
indicated by the dotted lines in Figure 2, Sheet 11, and meets its
fellow dorsal to the liver. Each arch gives off subclavian arteries to the
limbs, and the left, immediately before meeting the right, gives off the
coeliaco-mesenteric artery [to the alimentary canal]. This origin of the
coeliaco-mesenteric artery a little to the left, is the only asymmetry
(want of balance) in the arterial system of the frog, as contrasted with
the very extensive asymmetry of the great vessels near the heart of
the rabbit. [Posteriorly the dorsal aorta forks into two common iliac
arteries (right and left) supplying the hind limbs.]

Section 10. Figure 3 gives a side view of the frog, to display the
circulation.

{Lines from Second Edition only.}
[The venous return to the heart, as in the rabbit, is by paired venae
cavae anteriores and by a single vena cava inferior. The factors of the
anterior cava on either side are an external jugular (ex.j.) an
innominate vein (in.v.) and subclavian (scl.v.). The last receives not
only the brachial vein (b.v.) from the fore limb, but also a large vein
bringing blood for the skin, the cutaneous (p.v.). The innominate vein
has also two chief factors, the internal jugular (l.i.j.v.) and the
subscapular (s.s.v.). The blood returns from each hind limb by a
sciatic (l.sc.) or femoral (f.m.) vein, and either passes to a renal portal
vein (l.r.p.), which breaks into capillaries in the kidney, or by a paired
pelvic vein (l.p.v. in Figures 1 and 3) which meets its fellow in the
middle line to form the anterior abdominal vein (a.ab.v.) going forward
and uniting with the (median) portal vein (p.v.) to enter the liver.]

-The vessels are named in the references to the figure, which should
be carefully