568 DR. J. MURIE 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 vitulina &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, 
Pl. LX XXL. 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 from 0-2 to 0°5 or 06 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 
circumferentially, 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 widish 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, 
divides 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 differentiated. 
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. 
