BLOOD VESSELS 



413 



intestine, joins the caudal, and immediately after it has separated 

 from its fellow the hypogastric receives an internal iliac vein. 

 In its course through the kidney it receives several small renal 

 veins and a sciatic. There is a small renal portal system, the 

 femorals giving a few branches to the kidneys. A hepatic portal 

 system exists as usual. A vein, usually known as the epigastric, 

 takes blood from the great omentum, or sheet of fat which covers 

 the abdominal viscera, to the left hepatic vein. It represents the 

 anterior abdominal vein of the frog. There is much variation in 

 the details of the vascular system of different species of birds. 



EXCRETORY AND REPRODUCTIVE ORGANS 



The kidneys are metanephric (pp. 615 — 619). They lie in the 

 back under the sacrum as a pair of three-lobed bodies (Figs. 327, 

 328). From the hinder lobe of each a ureter runs back to the 

 cloaca. There is no bladder. Nitrogen is excreted as uric acid, 

 not urea. The urine is very concentrated and in the cloaca the 



S R. 



r/r<?. 



Fig. 327. — The urogenital or- 

 gans of a female pigeon. — 

 From Thomson. 



K,, Kidney (metanephros) with three 

 lobes ; u., ureter ; cl., cloaca ; ov., 

 ovary ; od., oviduct ; ft., funnel at 

 end of oviduct ; r.r.od., rudinjentary 

 right oviduct. 



Fig. 328. — The urogenital 

 organs of a male pigeon. 

 — From Thomson. 



T., Testes ; V., base of inferior vena 

 cava ; S.R., suprarenal glands ; 

 K., kidneys with three lobes 

 (i, 2, 3) ; u., ureter ; v.d., vas 

 deferens ; v.s., seminal vesicle 

 d., cloaca. 



