Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Todd, Robert Bentley
tical (b) and a medullary substance (e),the latter 
terminating in a mamillary process (d) which 
is received into an infundibular offset from the 
ureter. All the lobules are thus connected 
with the ureter, forming a clustered mass like 
a bunch of grapes. The entire kidney is 
invested by a cellular capsule (e), a deep layer 
of which (f) passes into the fissures between 
the lobules, and in the substance of this interlo¬ 
bular tissue the vessels are imbedded. There 
is no anastomosis between the blood-vessels 
of neighbouring lobules, as shown by the cir¬ 
cumstance that when the artery in any of 
them has been obstructed in an injected pre¬ 
paration they remain uninjected.* This form 
of kidney is observed in amphibious Carnivora, 
as the otter and the seal tribes ; it is also found 
in the bear, and still more remarkably in the 
cetaceans. The lobular division of the kidney, 
which in these animals is a persistent condition, 
exists in the embryo of all the mammalia. In 
process of development in the greater number 
of genera, the lobules coalesce, and thus form 
a solid glandular organ having a smooth con- 
tinuous surface, and presenting in the normal 
state no trace of the original lobular divisions. 
The kidney of the ox presents a condition 
intermediate between the lobulated kidney and 
the solid organ of man and most other mam- 
miferous genera. In this animal the medullary 
portion of the kidney has coalesced, while the 
cortical part is marked out by deep interlobu¬ 
lar fissures. The coalescence of the lobules 
appears to have been arrested at a certain 
period of its progress. The manner in which 
the tubes open into the pelvis of the solid 
kidney admits of some variety. In some 
genera they open on a continuous concave 
surface, as in the horse and ass ; in others 
on a continuous ridge, as in the dog. A more 
common termination is in a conical projection, 
the apex of which is received into a calyciform 
cavity in the pelvis of the kidney. In some 
genera, as in the human subject, there are 
several of these conical processes in each 
kidney ; while in other animals, all the tubes 
of the gland converge to a single cone, as in 
the lion, the racoon, the kangaroo, the monkey, 
the squirrel, &c. 
The renal artery, derived from the abdominal 
aorta, enters the hilum of the kidney. The 
veins generally follow the arteries, but there 
are exceptions to this rule. In the lion kind 
the cat kind, as also in the hyaena and in the 
seal, perhaps one half of the veins yet on the 
external surface, over which they pass, enclosed 
in a doubling of the capsule, and so join the 
trunks from the inside just as the latter are 
passing out from the hilum. j* 
We now proceed to give a detailed account 
of the anatomy of the human kidney, with 
such facts in the minute structure of the gland 
in certain of the lower animals as serve to 
* This is seen in the kidney of a walruss, No. 
1265 in the Museum of the College of Surgeons. 
•j- Hunterian Museum and Catalogue. 
throw light upon the structure and office of 
this important organ in man. 
Form.—The form of the kidney being so 
familiar as to serve for a standard of compa¬ 
rison with other objects, it appears needless to 
speak of its resemblance to a French bean, 
the concave margin being directed towards 
the spine, while the convex margin, which is 
thick and rounded, is directed outwards. 
The upper extremity is usually broader and 
thicker than the lower. The anterior surface 
is convex ; the posterior is flatter and rests 
upon the muscles and fascia. The two kid¬ 
neys are occasionally, but very rarely, united 
by a band of renal substance, extending 
transversely across the spine in front of the 
aorta. The two glands thus united have the 
form of a horse-shoe, the concavity of which 
is directed upwards. 
Dimensions and 'weight.—The average length 
of the kidney is from 4 inches to 4£ inches, 
its breadth 2 inches, and its thickness 1 inch. 
Its usual weight is from 3 to 4 ounces. 
Position and relations.—The kidneys are 
situated deeply in the lumbar region on each 
side of the spine, occupying a space corre¬ 
sponding to the last dorsal and the two or 
three upper lumbar vertebræ. The right is 
usually somewhat lower than the left, being 
depressed, as it were, by the liver, which is 
placed just above it. Occasionally one or 
both kidneys may be found very much out of the 
natural position, being situated either in front 
of the spine, or much below the usual posi¬ 
tion, even as low as the cavity of the pelvis. 
The kidneys are placed somewhat obliquely, 
the upper extremities being inclined towards 
the spine and approaching nearer to each 
other than the lower. They are imbedded 
in a layer of adipose tissue, the quantity of 
which is very variable, being thick and abun¬ 
dant in fat subjects, while in those who have 
died much emaciated, the loose investment 
of reticular tissue presents scarcely a trace 
of fat. 
The anterior surface of each kidney looks 
somewhat outwards ; it is partly covered by 
the peritoneum, chiefly at the upper extre¬ 
mity, and more on the right side than on the 
left. The right kidney is covered by the 
ascending colon, and the left by the descending 
colon. The anterior surface of the right 
kidney is also in contact with a small portion 
of the duodenum, and is covered by the right 
lobe of the liver. In some instances the gall¬ 
bladder covers a large part of the anterior 
surface of the right kidney. The left kidney 
at its upper part lies in contact with the 
spleen, and is covered by the great end of the 
stomach when this viscus is distended. 
With reference to diagnosis, it is important 
to bear in mind the proximity of the kidneys 
to the colon, and the possibility of disease ex¬ 
tending from one organ to the other. Ab¬ 
scess of the kidney has in many instances 
been known to burst into the colon, and it is 
not improbable that ulceration of the colon, 
either simple or malignant, might extend 
backwards into the kidney.


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