568 DE. J. MUEIE ON THE ANATOMY OF THE SEA-LION. 



flattened, oval form, rather blunted, however, at the extremities ; the hilus, as the 

 kidney lies in situ, appears shallow, and has a somewhat forward or ventral direction. 

 The two kidneys are situated almost on a level with each other, near the middle of the 

 loins. The renal arteries, as has been mentioned, enter the hilus at right angles, 

 while the emulgent veins of enormous calibre leave it more obliquely, and pass rather 

 forwards ; the ureters, most deeply situate, diverge at an opposite angle from the veins. 



The capsular tunic is a strong, firm, fibrous membrane, pierced and ramified by 

 numerous small vessels, chiefly arterial, but not possessing an external network of large 

 veins as obtains in Phoca mtulina &c. Covered by its capsule, each kidney has a 

 roughened aspect, indicating lobulation, but this by no means prominent. When the 

 capsule is removed, the superficial renal lobulations become more manifest, the furrows 

 and ridges, however, still being shallow and imperfectly defined. 



As in feline animals generally, the external cortical substance of the kidney, when 

 injected, presents a peculiar and rather beautiful arborescent vascular tracery. This 

 dendritic appearance, shown in fig. 71, is due to the ramification of minute veins upon 

 the surface of each renule; the arterial capillaries are not so distinct and not so 

 numerous, but they nevertheless form an intervening complementary set of ramifications. 



If a longitudinal section is made a little to one side of the median line, as fig. 70, 

 PI. LXXXI. illustrates, the kidney there is seen to be composed of between fifty and 

 sixty lobules or renules of an irregular pentagonal and hexagonal figure, and varying in 

 size fi-om 0-2 to 0-5 or 0-G of an inch. Each renule, though closely adherent to its 

 neighbour, is clearly defined into its three renal constituents. In the middle and 

 widest space are the fine and straight tubuli uriniferi, which radiate outwards ; these 

 are surrounded by a narrow arterial ring of short radiant vessels in which here and 

 there puncta indicate the Malpighian corpuscles. Lastly, bounding the arterial ring 

 circumferentiaUy, is a rather broader venous band, which is common to the several 

 adjoining lobules, and, as mentioned, has an arborescent cortical configuration. Each 

 renule manifests its independent structure in the uriniferous tubules terminating in a 

 papilla, projecting into a central cavity, which in the section in question is only dis- 

 played in some of the lobules. The cavities communicate with ^vidish infundibular 

 tubes, which convey the urine to the pelvis of the kidney, the latter being deeper on 

 section than its outward appearance warrants. The renal artery, as it reaches the hilus, 

 dindes into several branches, which again subdivide into the lesser ramifications. The 

 veins return the blood, in channels parallel with these, to the very wide emulgent vessel. 



Previously to making the above-described section, I forced successfully into the kidney 

 a fine injection of three different colours, viz. red into the artery, blue into the vein, 

 and yellow into the ureter. By this method the structures were well difierentiated. 

 A whole kidney thus manipulated is now preserved in the Hunterian Collection ; and a 

 half of the other has been mounted by Mr. J. W. Clark, and is now deposited in the 

 Zoological Museum of Cambridge. 



