THE KIDNEYS. 993 



in their course the efferent vessels from the Malpighian bodies in the cortical 

 structure adjacent, quit the kidney substance to enter the sinus. In this cavity 

 they inosculate with the corresponding veins from the other pyramids to form the 

 renal vein, which emerges from the kidney at the hilum and opens into the inferior 

 vena cava, the left being longer than the right, from having to cross in front of 

 the abdominal aorta. 



Nerves of the Kidney. The nerves of the kidney, although small, are about 

 fifteen in number. They have small ganglia developed upon them, and are derived 

 from the renal plexus, which is formed by branches from the solar plexus, the 

 lower and outer part of the semilunar ganglion and aortic plexus, and from the 

 lesser and smallest splanchnic nerves. They communicate with the spermatic 

 plexus, a circumstance which may explain the occurrence of pain in the testicle in 

 affections of the kidney. So far as they have been traced, they seem to accompany 

 the renal artery and its branches, but their exact mode of termination is not 

 known. 



The lymphatics consist of a superficial and deep set which terminate in the 

 lumbar glands. 



Connective Tissue, or Intertubular Stroma. Although the tubules and vessels 

 are closely packed, a certain small amount of connective tissue, continuous with 

 the capsule, binds them firmly together. This tissue was first described by Goodsir, 

 and subsequently by Bowman. Ludwig and Zawarykin have observed distinct 

 fibres passing around the Malpighian bodies, and Henle has seen them between 

 the straight tubes composing the medullary structure. 



Surface Form. The kidneys, being situated at the back part of the abdominal cavity and 

 deeply placed, cannot be felt unless enlarged or misplaced. They are situated on the confines 

 of the epigastric and umbilical regions internally, with the hypochondriac and lumbar regions 

 externally. The left is somewhat higher than the right. According to Morris, the position of 

 the kidney may be thus defined: Anteriorly: "1. A horizontal line through the umbilicus is 

 below the lower edge of each kidney. 2. A vertical line carried upward to the costal arch from 

 the middle of Poupart's ligament has one-third of the kidney to its outer side and two-thirds to 

 its inner side i. c. between this line and the median line of the body." In adopting these lines 

 it must be borne in mind that the axes of the kidneys are not vertical, but oblique, and if con- 

 tinued upward would meet about the ninth dorsal vertebra. Posteriorly : The upper end of the 

 left kidney would be defined by a line drawn horizontally outward from the spinous process of the 

 eleventh dorsal vertebra, and its lower end by a point two inches above the iliac crest. The right 

 kidney would be half to three-quarters of an inch lower. Morris lays down the following rules 

 for indicating the position of the kidney on the posterior surface of the body : "1. A line par- 

 allel with, and one inch from, the spine, between the lower edge of the tip of the spinous pro- 

 cess of the eleventh dorsal vertebra and the lower edge of the spinous process of the third 

 lumbar vertebra. "2. A line from the top of this first line outward at right angles to it for 

 '2 ; inches. 3. A line from the lower end of the first transversely outward for 2| inches. 4. A 

 line parallel to the first and connecting the outer extremities of the second and third lines just 

 described." 



The hilum of the kidney lies about two inches from the middle line of the back, at the level 

 of the spinous process of the first lumbar vertebra. 



Surgical Anatomy. Malformations of the kidney are not uncommon. There may be an 

 entire absence of one kidney, though, according to Morris, the number of these cases is "exces- 

 sively small " : or there may be congenital atrophy of one kidney, when the kidney is very small, 

 but usually healthy in structure. These cases are of great importance, and must be duly taken 

 into account, when nephrectomy is contemplated. A more common malformation is where the 

 two kidneys are fused together. They may be only joined together at their lower ends by means 

 of a thick mass of renal tissue, so as to form a horseshoe-shaped body or they may be completely 

 united, forming a disc-like kidney, from which two ureters descend into the bladder. These 

 fused kidneys are generally situated in the middle line of the abdomen, but may be misplaced 

 as well. 



One or both kidneys may be misplaced as a congenital condition, and remain fixed in this 

 abnormal position. They are then very often misshapen. They may be situated higher or lower 

 than normal or removed farther from the spine than usual or they may be displaced into the 

 iliac fossa, over the sacro-iliac joint, on to the promontory of the sacrum, or -into the pelvis 

 between the rectum and bladder or by the side of the uterus. In these latter cases they may 

 give rise to very serious trouble. The kidney may also be misplaced as a congenital condition, 

 but may not be fixed. It is then known as a floating kidney. It is believed to be due to the 

 fact that the kidney is completely enveloped by peritoneum which then passes backward to the 

 spine as a double layer, form ing a mesonephron, which permits of movement taking place. The 

 kidney may also be misplaced as an acquired condition ; in these cases the kidney is mobile in 

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