THE POSTUBIOB AORTA. 631 



Such is the general arrangement of the arteries of the email intestine; 

 and it remains to indicate some of their special characters, which are as 

 follows : 1, The longest arteries of the small intestine are the most posterior, 

 as^ they follow the development of the mesentery, by which they are sus- 

 tained ; 2, The anterior arteries generally form two series of superposed 

 arches, before sending their divisions to the intestine ; 3, The first reaches 

 the duodenum and anastomoses with tlie duodenal artery — a branch given off 

 by the coeliao axis ; 4, The last cominnnicates with the ileo-c£Bcal artery — one 

 of the branches of the right fasciculus. 



B. Aetbries of the Eight Fasciculus. — The right fasciculus of the 

 great mesenteric artery constitutes, at first, a single truck some inches in 

 length, which soon divides into four branches ; these are as follows : the 

 ileo-ccecal artery, the two ccecal arteries, and the right or direct colic artery. 



Ileo-C^oal Arteet (Fig. 271, 3). — ^This vessel often has its origin 

 from the internal cseeal artery. It is placed between the two layers of the 

 mesentery, follows for a short distance, and in a retrogade manner, the ileo- 

 csecal portion of the small intestine, and wholly anastomoses with the last 

 artfery of the left fasciculus, after emitting a series of branches, which are 

 distributed to the intestinal membranes. 



C*OAL Aeteeies, — Distinguished into internal or superior, and external 

 or inferior, these two arteries pass downward and a little to the right, 

 towards the concavity of the cseeal ilexure, embracing between them the 

 terminal extremity of the small intestine, and lying at the middle part 

 of the cseeal sac, whose direction they follow. 



The superior, or internal ccecal artery, is lodged in the most anterior 

 of the fissures formed by the longitudinal bands of the CEecum, and extends 

 beneath the serous tunic to nearly the point of the viscus, where it terminates 

 by anastomosing with the external cseeal artery. The branches furnished 

 by this artery during its course escape in a perpendicular direction, and 

 distribute their ramifications on the walls of the csBcum (Fig. 271, 4). 



The external, or inferior cseeal artery, passes between the csecum and the 

 origin of the colon, to descend along the first-named receptable by placing 

 itself in one of the external fissures, which is situated outwardly and 

 posteriorly. Arriving at the point of the organ, this artery bends over it to 

 anastomose with the vesseljust described (Fig. 271, 7). It gives off on its 

 track a series of transverse ramifications, similar to those of the latter artery ; 

 and besides these, a remarkable branch which may be named the artery of 

 the ccecal arch. This branch is detached from the principal vessel near the 

 origin of the colon, and ascends to the csBcal arch, whose concavity it follows 

 outwardly to pass forwards and downwards to the initial portion of the large 

 colon, where it disappears after following a certain course. The numerous 

 collateral branches detached by this artery are sent to the walls of the latter 

 portion of intestine, and the arch of the cEBCum (Fig. 271, 6j. 



Eight or Direct Colic Abtery (Fig. 271, 7). — This is the largest of 

 the branches composing the right fasciculus of the great mesenteric artery. 

 Destined for the right portion of the flexure formed by the large colon, it 

 lies immediately beside that viscus, beneath the peritoneal, membrane, 

 following it from its origin to its pelvic curvature, where the artery 

 anastomoses by inosculation with the left colic or retrograde artery. 



C. Aeteeies op the Anteeioe Fasciculus. — These are only two in 

 number: the left colic or retrograde, and ilne first artery of the small colon, 

 joined at their origin to an extremely short trunk. 



Left Colio ob Eeteogkade Arteey (Fig. 271, 8). — This is carried 



