THE URINARY SYSTEM: KIDNEYS 431 



adult. It appeared, from the examination of single sections, to resemble that found in 



other mammals — a convoluted portion and an ascending and descending portion were 



observed. 



The vascular supply 



The post-caval veins (Fig. 22 f 1 ,/ 2 ), returning blood from the lumbar regions, run on 

 either side of the dorsal aorta, parallel with it. At a point about one-third of the length 

 of the left kidney from its anterior end, and about half the length of the right, the two 

 post-cavae change their direction. The left member of the pair turns towards the middle 

 line at an angle of about 45 , while the right bends inwards at a slightly smaller angle. 

 The two great veins join to form a common trunk a little to the right of the dorsal 

 aorta (Fig. 22 e). The great post-caval trunk so formed runs from its commencement, 

 about one-third the length of the right kidney from its anterior end, and after running 

 for a short distance forwards parallel with the aorta, penetrates the diaphragm to the 

 right and a little ventral of the point of emergence of the aorta (Fig. 22 e). The course 

 of the aorta is as usual straight down the mid-dorsal line of the roof of the abdominal 

 cavity. 



The renal arteries (Fig. 22 h 1 , h 2 ) are single on each side and run obliquely to their 

 entrance into the kidneys — that on the right side being in advance of that on the left by 

 a distance equal to that which separates the level of the tip of the right kidney from the 

 level of the tip of the left. The renal arteries enter the kidneys on their mesal faces at a 

 point about one-third the length of each from its anterior end. At their point of entrance 

 the arteries are involved in the serous mesentery and form the most anterior point of the 

 mesal slit. Beauregard and Boulart found one large and one small renal artery on each 

 side. In the Cetacea in general there are frequently two renal arteries on each side of 

 equal importance, as in Hyperoodon (Bouvier, 1892). In the dolphin (Anthony, 1922) 

 there are two large arteries on the right side and several small ones on the left. 



The renal veins (Fig. 22 g x , g 2 ) leave the kidneys at the anterior extremities of the 

 mesal faces in company with the arteries. They lie anterior to the arteries and show a 

 distinct tendency towards the plexiform arrangement which appears to be general in 

 the venous system of the Cetacea. There are usually two or three stout veins emerging 

 from the interior of the kidney by the mesal slit, and these are joined by a number of 

 smaller veins from a venous network covering the whole of the outside of the organ 

 within the fibrous investments. The origin of this peripheral network, from lacunae 

 between the serosa and the capsula fibrosa, has already been mentioned (p . 4 1 6). The stout 

 veins from the interior and the smaller ones from the superficial network may join together 

 to form a common trunk before entering the postcava, or may enter it severally as one or 



Fig. 30. Diagrams to show the arrangement of the capsules and tubules in the Fin whale in : A. A lobe with 

 three lobules of the kidney of a Blue whale foetus 18-5 cm. in length. B. One young renculus of the kidney 

 of a Fin whale foetus 0-9 m. in length. Note that the capsules are showing signs of their future peripheral 

 disposition. 



a. Interlobar septum. d. Tunica albuginea. 



b. Interlobular septum. e . Main collecting tube of the renculus (Tertiary 



c. Serosa. urinary duct or calix). 



