670 URINARY APPARATUS. 



is most frequently noticed in the right kidney, the left being generally like the 

 first. 



Flattened on both sides, the kidneys show two perfectly smooth faces, the 

 inferior of which always exhibits a variable number of furrows that lodge the 

 arteries ; the right kidney has always a special furrow for the ureter. Each 

 kidney has a circumference divisible into three borders, only the internal of 

 which offers a certain interest. This is deeply notched, to form the fissure or 

 Mlus of the kidney, which lodges the vessels and nerves of the organ, as well as 

 the origin of the ureter. 



Weight. — The kidneys vary much in weight in individuals. The right is 

 always more voluminous and heavy than the left, its average weight being 

 27 ounces, while that of the last is 25 ounces. 



Relations. — The relations of these two glands with the neighbouring parts 

 ought to be particularly examined. The right kidney is related, by its upper 

 face, to the great psoas muscle, the muscular portion of the diaphragm, and to 

 the last, or even the second-last rib. Its inferior face, incompletely covered by 

 peritoneum, adheres, for the greater part of its extent, either to the pancreas and 

 supra-renal capsule, or to the base of the caecum, by means of a loose and 

 abundant connective tissue. The internal border is in contact with the posterior 

 vena cava and the small psoas muscle ; the anterior, with the base of the right 

 lobe of the liver and the lobule of Spigel {lobus caiidatus), through the medium 

 of the peritoneum ; the posterior border is enveloped in peritoneum. The left 

 kidney has, by its superior face, the same connections as the right, except in its 

 relation with the second last rib. Its inferior face is almost entirely covered by 

 peritoneum, and is related, in front and inwardly, to the supra-renal capsule. 

 The internal border is margined by the aorta ; the anterior touches the base of 

 the spleen and the left extremity of the pancreas ; the posterior is, like the 

 inferior face, in contact with the serous membrane of the abdominal cavity. 



Internal conformation. — If a horizontal section is made of the kidney, it will be 

 found to possess a cavity called the renal basin (or pelvis), into which the urine 

 secreted by the gland flows, and at which the ureter commences. Placed in the 

 middle of the kidney, near the hilus, the pelvis is elongated before and behind, 

 and depressed from above to below. Within it is remarked a wide infundibulum — 

 the origin of the ureter (the sinus renalis). Opposite to this funnel-shaped space 

 is a very prominent crest {renal crest) that rims along the whole length of the 

 external side of the pelvis, and on which are noticed the orifices of the uriniferous 

 tubes ; these, by pressing the tissue of the kidney with the fingers, can be made 

 to pour out the urine accumulated in them. The renal cavity forms some very 

 small diverticuli opposite the infundibulum, the largest of which — situated before 

 and behind the latter — are named the arms of the pelvis. 



This cavity is lined by a transversely plicated mucous membrane, continuous 

 with that of the ureter, and is covered with the epithelium of the uriniferous 

 tubes which open on the border of the crest. At these folds, the mucous mem- 

 brane contains small racemose glands lined by two layers of cells (Paladino and 

 Egli). 



Structure. — The kidneys present for study in their structure : 1. An 

 enveloping tunic. 2. Their proper tissue. Z. Vessels &n& nerves. 



1. Enveloping Tunic. — This is a fibrous membrane, intimately united to 

 the proper substance of the kidney, into which it sends a multitude of prolonga- 

 tions, and is folded around the blood-vessels in such a manner as to form sheaths, 



