234. 



REN. 



tical (6) and a medullary substance (c), the latter 

 terminating in a mamillary process (r/) whicli 

 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 (/) 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 tabulated 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 hyasna 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.f 



PART II. THE HUMAN KIDNEY. 



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. 

 12G5 in the Museum of the College of Surgeons, 

 f Ilunterian 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 4-1 inches, 

 its breadth 2 inches, and its thickness 1 inch. 

 Its usual weight is from 3 to -i 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 vertebrae. 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 maybe 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 



~ ^ J o 



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 visctis 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 ulceratiou of the colon, 

 either simple or malignant, might extend 

 backwards into the kidney. 



