j | THE KIDNEYS. 1085 
and is the hepatic impression (impressio hepatica); another stretches from the most 
prominent point to the lower end of the kidney, and is related to the colon; while 
the third extends along the inner margin, below the hilus, and is in contact with 
the second part of the duodenum (Fig. 730). 
On the left kidney, also, three more or less marked, flattened impressions slope 
towards the borders of the organ from the most prominent part of the anterior 
surface. One of these, on the upper and outer part of the kidney, is the splenic 
impression ; another, extending downwards to the lower end of the kidney, is for 
the colon, or for the colon and jejunum ; while the third, or impressio gastrica, corre- 
sponds to the position of the overlying stomach. The gastric impression occupies 
an area of the anterior surface of the left kidney, above and in the region of the 
hilus. Only a small portion of this impression is directly in contact with the 
stomach, since the pancreas and a part of the suprarenal capsule intervene between 
the stomach and the kidney (Fig. 730). 
It is common to find the left kidney thicker and less flattened antero-posteriorly than 
the right, the impressions, or facets, upon its surface being at the same time better 
marked. With this is probably to be associated the fact that floating kidney is more rarely 
met with on the left side than on the right. 
Extremities of the Kidney.—Jhe kidney, fixed and hardened in. situ, is 
usually more pointed at its dower than at its wpper end. The latter is more 
flattened from before backwards, and wider from side to side. This flattened part 
of the kidney rests upon the diaphragin, and is bent somewhat forward. 
Renal Sinus (sinus renalis)—The sinus of the kidney (Fig. 731), into 
which the hilus opens, is a narrow space, having its long axis corresponding to 
that of the kidney. The thick . 
walls of the sinus cavity are formed 
by the substance of the kidney, and 
lined by a part of the fibrous kidney 
capsule which enters the sinus over 
the lips of the hilus. The floor of 
the sinus is not smooth, but pre- 
sents a series of small projecting 
conical elevations called renal 
papillae (papille renales), which Pyramid——= 
vary from twelve to fifteen im Column of | 
Sore , Bertin 
number. Radiating from each wanorsinus 
papilla are a number of bars or 
ridges of kidney substance, some- acne | 
what raised, and having depressed Bertin” | 
areas between them. The blood- JID 
4. Pyramid 
vessels and nerves enter and leave 
the kidney by piercing the wall of 
the sinus where it is formed by 
these little depressed areas. When 
the vessels and nerves are removed 
these depressions present a eribri- 
form appearance (are  cribrosze, 
Fig. 731). The summit of each The vessels and fat have been removed to give a view of the 
renal papilla is pierced by a num- wall of the kidney sinus. The points where the vessels 
ber of minute openings calle «1 fora- enter the kidney sinus are seen as little holes in the sinus 
wall at a and elsewhere. 
mina papillaria. These are the 
terminal apertures of the secreting tubules, of which the kidney is to a large 
extent composed, and the urine secreted by the kidney escapes through them into 
the upper part of the ureter. 
Kidney in Section.—Sections (Fig. 731) through the kidney show it to be, 
for the most part, composed of a number of pyramidal masses arranged with their 
bases towards the surface, while their apices project into the sinus of the kidney 
and form the renal papillze already described. These masses of kidney substance 
Papilla 
I 
Fig. 731.—LoNGITUDINAL SECTION THROUGH THE KIDNEY. 
