_1_, Anterior mesenteric artery; _2_, middle colic artery; _3_,
ileo-cæco-colic artery; _4_, ramus collateralis; _5_, continuation
of anterior mesenteric artery, giving off branches to small
intestine; _6_, cæcal artery; _7_, colic branch of posterior
mesenteric artery; _A_, termination of duodenum.
]
The two preceding vessels are essentially the arteries of the small
intestine, which they supply with the exception of its initial and
terminal parts. The first gives off no considerable branches in its
course along the ventral border of the coils of the colon, but on
curving upward along the latter it anastomoses with the second artery
and detaches numerous branches to the small intestine which form series
of superposed anastomotic arches. It supplies, roughly speaking, about
one-third of the small intestine and terminates by joining the ileal
artery. The second artery gives off numerous branches which also form
arches and supply about the first two-thirds of the small intestine,
exclusive of the small part supplied by branches of the cœliac artery.
Both arteries give branches to the lymph glands.[181]
The =posterior mesenteric artery= arises from the aorta near its
termination. It is small and supplies branches to the terminal part of
the colon and to the rectum.
The =renal arteries= arise from the aorta close together. The right one
passes outward and forward across the dorsal face of the posterior vena
cava to the hilus of the kidney. The left one runs backward, but
necessarily varies in direction in conformity with the position of the
kidney (_q. v._).
The =spermatic arteries= resemble those of the horse.
The =utero-ovarian arteries= are small.
The five pairs of =lumbar arteries= derived from the aorta are
distributed much as in the horse. The sixth usually comes from the
internal iliac artery.
[Illustration: