1894.] ANATOMY OF OENITHORHTNCHTJS. 713 



This divides at once into the following branches proceeding from 

 without inwards : — 



A slender branch to bladder. This is Hyrtl's cystic artery. 



A large branch, which runs downwards and backwards ; leaves 

 pelvis beneath symphysis pubes ; runs down on the side of the 

 rectum, and is distributed to the penis and to Cowper's gland. 

 This may represent internal pudic ; it gives off branches to bladder, 

 rectum, and an artery, which divides into a pencil of fine vessels 

 and passes to the under surface and side of middle of tail. This 

 artery Hyrtl speaks of as the common pudendal. 



A pencil of fine vessels, four in number, which descend into 

 the pelvis parallel to each other, soon subdivide, and passing 

 from thence are eventually distributed to the sides of the tail. 

 This pencil has divided into a set of ten or twelve fine vessels at 

 the side of the anterior part of caudal region. 



The innermost of the three trunk branches divides at once into 

 three vessels ; these descend into pelvis parallel to each other, and 

 emerging from thence are distributed to the gluteal region ; the 

 largest of the three passes to the back of the thigh. These arteries 

 represent gluteal and sciatic. 



The central caudal artery descends in the middle line to tip of 

 tail. 



The whole arrangement is repeated on the opposite side. 



Branches of the Trunk Aorta. 

 The only branches given off from thoracic trunk are the inter- 

 costal arteries. These are nine in number on each side. The 

 first supplies the third and fourth spaces, running along the line 

 of the fourth rib and giving off branches anteriorly and posteriorly 

 to third and fourth spaces. The fifth to the twelfth intercostal 

 intervals are supplied by the second, third, fourth, fifth, sixth, 

 seventh, and eighth arteries. The thirteenth, fourteenth, and 

 fifteenth intervals are supplied by the ninth aortic intercostal. 

 The sixteenth interval is supplied by the first and second lumbar 

 arteries. The upper two spaces are supplied by a superior inter- 

 costal. There are five lumbar arteries. They come off by a 

 common trunk which immediately divides into the arteries of 

 opposite sides ; the first and second supply the last intercostal 

 spaces ; the others are quite below the ribs ; the last one passes 

 backwards to the posterior surface of the sacrum and traverses 

 the sacral arcade of Howes l . 



Visceral Brandies. 



There is a cceliac or ccelio-mesenteric axis dividing into gastro- 

 hepatic, splenic, and superior mesenteric. They are distributed to 

 the structures indicated by their names. 



Renal arteries. — There are two short renal arteries, which are 

 not very large. Midway between the renal and the division of 

 the aorta is a slender spermatic artery which is extremely tortuous. 



1 'Journal of Anatomy and Physiology,' vol. vii., n. s., 1892-93. 



