aii 
THE KIDNEYS. 1087 
Vessels of the Kidney.—The renal artery is very large in proportion to the size 
of the organ to which it conveys blood. Its terminal branches, as they approach the 
kidney to enter the hilus, lie betw een Labyrinth Medullary ray 
the tributaries of the renal vein in | 
front and the ureter behind. Enter- 
ing the substance of the kidney ‘in 
the manner described above (page 
1085), the larger branches lie in the 
intervals between the pyramids, and 
are called the interlobar arteries 
—Glomerulus 
—Labyrinth 
— Interlobular 
artery 
(arteriz interlobares renis). These — Cp arer cine 
vessels dividing, form a series of in- Per 
complete arterial arches (arteriz arci- ~ arch 
formes), which pass across the bases 
of the pyramids. From the arches 
two chief sets of branches come off Ser 
—those of one set are continued to- 
wards the periphery and enter the Collecting 
labyrinth, while those of the second bube 
set pursue a recurrent course and ; 
enter the intermediate zone of the ae 
medulla. The latter vessels, called 
° : ¢ Efferent 
arteriole rectz, give rise to the — vessel 
coarsely - striated appearance which Afferent 
this part of the kidney exhibits in WEES 
section. Each of these vessels, en- *\Glomerulus 
tering the medulla, divides into a 
number of fine branches which run 
nearly parallel to one another, and Kia, 733.—DIAGRAMMATIC REPRESENTATION OF THE 
supply the tubules in this region of SHIRTOIO CIELO UNG EREN Gs ASUS Neve Lore 
the kidney. The vessels directed out- !" the middle part of the figure the course of one of the kidney 
nS ae : SA): tubules is indicated, and in the lateral parts the disposition 
wards, or interlobular arteries (ar terle ap the larger arteries. A, Cortex ; B, Intermediate zone ; 
Capsule 
Pee alunos), pass through the laby- ! Papillary portion. 
riuth towards the surface of the kidney. The deen at the right-hand side of the lower part of the 
They give off a number of short figure illustrates the connexions of the structures com- 
sing a Malpighian corpuscle. 
branches, termed vasa afferentia, each posing way Mal piohit ieoupuscle 
of which proceeds to the dilated extremity, or capsule, of a uriniferous tubule. Here the 
vas afferens breaks up into a much convoluted capillary mass, called a glomerulus, which 
is contained within the invagination of the capsule. The little vein which issues from 
the glomerulus is termed a vas efferens; but instead of running directly into a larger 
vein, it breaks up, after the manner of an artery, into capillaries w yhich supply the tubules 
of the labyrinth and medullary rays. The tubules of the intermediate zone also receive 
their blood-supply from the vasa efferentia of the nearer glomeruli. 
Veins corresponding to the interlobular arteries and arteriole rectze collect the blood 
from the capillaries surrounding the tubules, and unite to form a series of complete arches 
across the bases of the pyr: amids. From these venous arcades vessels arise, which, traversing 
the intervals between the pyramids, reach the sinus of the kidney, where they unite to 
form the tributaries of the renal vein. 
Nerves of the Kidney.—The nerves of the kidney accompany the branches of the 
arteries, and are derived from the renal plexus. 
Variations.—A marked difference in the size of the two kidneys is sometimes observed, a 
small kidney on one side of the body being usually compensated for by a large kidney on the 
opposite side. Cases of complete absence of one or other kidney are recorded. 
Traces of the superficial lobulation of the kidney, present in the foetus and young child, are 
often retained in the adult. 
Horse-shoe kidney is not an infrequent abnormality. In these cases the two kidneys are 
united at their lower ends, across the middle line, by a connecting piece of kidney substance. 
The amount of fusion between the two kidneys varies much ; ‘jt is sometimes very com- 
plete, while in other cases it is but slight, the connexion being chiefly composed of fibrous 
tissue. 
In some mammahan animals, such as the bear, the ox, the porpoise, ete, the kidneys are 
composed of a number of completely isolated lobes, each of which corresponds to one pyramid 
and its surrounding cortex ; while in others, such as the horse, the fusion of the lobes is more 
complete eyen than in the human kidney, and a single mass represents the united pyramids. 
