EXCRETION AND THE EXCRETORY ORGANS 465 



a little larger than the lower. From the abdominal aorta, A, a 

 renal artery, Ar, enters the inner border of each kidney, to break 



Vr 



u 



Fiq. 138. The renal organs, viewed from behind. R, right kidney; A, aorta; 

 Ar, right renal artery; Vc, inferior veme cavw; Vr, right renal vein; U, right 

 ureter; Vu, bladder; Ua, commencement of urethra. 



up within it into finer branches, ultimately ending in capillaries. 

 The blood is collected from these into the renal veins, Vr, one of 



