ORIGIN OF THE RENAL ARTERY 197 



renal gland. The rabbit utilizes as an inferior suprarenal artery 

 one of the upper lateral branches of the plexus, from the lower 

 end of which the renal sprouts develop, so that the suprarenal 

 artery, as well as the 12th intercostal artery, is normally a branch 

 of the renal, as stated by Gerhardt. Other animals may or may 

 not have such connections between renal and suprarenal arteries, 

 but in all cases the renal is the older vessel. 



In contrast to the other mammals examined the early develop- 

 ment and rapid growth of the suprarenal gland in man is very 

 striking. At 8.0 mm. (H.E.C. No. 877) while the kidney is 

 still a pelvic organ, the group of cortical cords has already grown 

 down to the level of the first lumbar arteries, or in other words is 

 occupying the region later to be invaded by the kidney. It 

 would be interesting to speculate, in connection with the work 

 of Cannon (18), on the activity of this gland in various emotions, 

 whether man is given an advantage over other mammals by its 

 precocious development; but that is at present beside the ques- 

 tion. The result, so far as the arteries are concerned, is that 

 the suprarenal gland primarily receives the vessels which in 

 other mammals go to the kidney. These arteries are at first 

 numerous, but only three survive, as was pointed out by Bro- 

 man (4) ; and it is only the most caudal of the three which is 

 immediately interesting. Broman states that the suprarenal 

 arteries are branches of the mesonephric vessels, but I must 

 disagree partially with this statement, for I have seldom seen 

 such a connection in the embryos examined. Normally all of 

 the suprarenal arteries are the lateral aortic roots of the plexus, 

 similar to the renal arteries already described in many mam- 

 mals. They never, in my specimens, extend to the mesonephric 

 glomeruli, nor are they branches of vessels which do, though 

 they are not infrequently connected by the anastomoses of the 

 plexus with the mesonephric arteries. Exceptionally a meso- 

 nephric artery does send a small branch to the suprarenal gland 

 but in the few cases I have seen, such branches are much smaller 

 than the normal arteries, though probably capable of persisting 

 under certain conditions. 



