TEE POSTERIOR AORTA. 621 



either from the aorta between the internal and external iliacs, or from the latter, 

 near its commencement. The last being the most common, it is usual to describe 

 it as a collateral branch of the external iliac trunk. We have regarded it as an 

 artery emanating directly from the posterior aorta, in order to include its descrip- 

 tion with that of the spermatic and the utero-ovarian arteries. 



Whatever may be its mode of origin, it gains entrance to the inguinal canal 

 with the spermatic vessels, to be distributed to the various p:irts constituting the 

 spermatic cord. Before penetrating the substance of this cord, it gives off several 

 ramuscules to the peritoneum, iliac glands, ureter, and vas deferens. 



Uterine Artery. — This has the same point of origin as the preceding — its 

 analogue — but differs from it in its larger volume. It is placed between the two 

 layers of the broad ligament, and soon divides into two branches — ovarian and 

 uterine. The ovarian branch is flexuous, like the corresponding artery in the 

 male, and comports itself on the ovary as that vessel does on the testicle. The 

 uterine branch passes to the cornu of the uterus, where its divisions anastomose 

 with the uterine artery proper. 



Differential Characters in the Posterior Aorta and its Collateral Branches is 



the other animals. 



Posterior Aorta in Ruminants. 



The artery pursues the same course as in Solipeds, and also ttrminates by four branches, 

 towards the entrance to the pelvic cavity. 



Parietal BRANCHts. — The intercostal arteries only differ from those of tlie Horse in their 

 number; as but twelve are met with, uf which eight or nine are furnished by the posterior 

 aorta alone. 



The lumbar and diaphragmatic branches are absolutely identical, in their disposition, with 

 the analotrous arteries in Solipeds. 



The middle sacral artery is more considerable in volume, particularly in the Sheep and 

 Goat. This will lie referred to hereafter (>pe Internal iliac artery of Ruminants). 



Visceral Branches Broncho-cesophageal trunk. — This offers notiiing particular. 



Cceliac axis (Fig. 367. 1). — This artery descends on the rumen, a little bihind the insertion 

 of the oesophagus, is directed to the right, and divides near the omasum into two terminal 

 brandies — tlie superior and inferior arteries of the omasum and abomasum. 



The collateral branches given off from this trunk are : — 



1. Several diaphragmatic arteries. 



2. Tlie splenic artery, almost exclusively destined for the spleen (Fig. 367, 8). 



3. The superior artery of the rumen, always arising from a very .«hort trunk common to it 

 and the preceding vessel, is carried backward to the superior face of the rumen, and from this 

 descends between the two conical vesicae, to anastomose with the artery of tiie inferior face of 

 the viscus (Fig. 3(;7, 2). 



4. The inferior artfry of the rumen, which is insinuated between the two anterior cw?s-rfe-8ac, 

 and afterwards runs along the inferior face of the organ, passing towards thi' notch separating 

 the two conical vesicae, to meet the superior vessels (Fig. 367, 3). 



5. The artery of the reticulum, has usually a common origin with the inferior artery of the 

 rumen, a-id passes forward on the left of the cesopluigus, to be divided, near the insertion of 

 that conduit, into two branches — one, the superior, inclines to the right on the small curvature 

 of the viscus (Fig. 367, 5); the other, the inferior, occupying the fissure separating the great 

 curvature of the reticulum from the right sac of the rumen, and giving to the latter organ a 

 gpreat number of branches (Fig. 367, 4). 



6. The hepatic artery, which is not only distributed to the liver, but also furnishes a branch 

 for the gall-bladder, and a duodenal art( ry breaking up into two branches — the posterior 

 branch forming with the first artery of the small intestine an arching anastomosis; the anterior 

 communicating with the superior artery of the omasum and abomasum. Tliis hepatic artery 

 always originates bt tween the trunk common to the splenic artery and the superior branch of 

 the rumen, and that which gives off the superior branch of the same viscus and the artery of 

 the reticulum. 



42 



