938 THE KIDNEYS. 



vein, which lies in front of the artery, and ends in the inferior vena cava 

 (p. 474). 



Nerves. The nerves which have been traced into the kidneys are small. 

 They come immediately from the renal plexus and the lesser splanchnic 

 nerve, and contain filaments derived from both the sympathetic and cerebro- 

 spinal systems. They may be traced accompanying the arteries to their finer 

 branches, but it is uncertain how they end. 



Intertubular Stroma. Between the tubules and vessels of the kidney, 

 although they are disposed closely together, a certain very small amount of 

 interstitial matrix exists, first described by Goodsir, then by Bowman and 

 others, and to which attention has latterly been paid by a number of 

 observers, and especially by Beer. This matrix is for the most part nearly 

 homogeneous, but has a more fibrous character in the vicinity of the rami- 

 fications of the blood-vessels. Fibres are likewise described by Ludwig and 

 Zawarykin as passing round the Malpighian corpuscles, and others have 

 been seen by Henle, coiling round the tubes of the medullary substance. 

 The stroma is more abundant in the cortical substance than in the greater 

 part of the medullary ; but according to Henle it is very abundant towards 

 the apices of the papillae. Nuclei and connective tissue corpuscles are scat- 

 tered through its substance. It is much more abundant in animals than in 

 man, and in the human kidney it is more apparent in the young than in the 

 adult, and is also much richer in corpuscles ; in this respect resembling the 

 connective tissue generally. 



Absorbents. The lymphatics of the kidney are numerous, consisting of a 

 superficial set, and of deep lymphatics which issue from the hilus with the 

 blood-vessels. According to the researches of Ludwig and Zawarykin, the 

 stroma of the kidney forms a thick network of freely intercommunicating 

 lymphatic spaces, guided to the surface along the tissue round the blood- 

 vessels. These spaces are similar to those previously found by Ludwig and 

 Tomsa in the testicle, and held by His to possess epithelial walls. They are 

 most abundant in the cortical substance. 



Among writings on the kidney, the following may be here referred to : Bowman, in 

 Philos. Trans. 1842; Toynbee, in Medico-Chir. Trans. 1846; Gerlach, in Muller's 

 Archiv, 1845; Johnson, article Ren, in Clyclopsedia of Anat. and Phys. ; Isaacs, in 

 Trans. New York Acad. of Medicine, vol. i., 1857 ; Henle, Zur Anatomic der Niere, 

 Gottingen, 1862, and in Handbuch; Ludwig and Zawarykin, in Wiener Kais, Acad. 

 Sitzungsbericht, vol. xlviii. 1864; Chrzonszczewsky, in Virchow's Archiv, xxxi. 1864; 

 Schweigger-Seidel, Die Niere des Menschen und der Saiigethiere. Halle, 1865 ; Southey, 

 in St. Bartholomew's Hosp. Reports, 1865; also, on the stroma, Goodsir, in Lond. and 

 Edin. Journ. of Med. Science, May, 1842 ; and Beer, Die Bindesubstanz d. Menschlichen 

 Niere, Berlin, 1859. 



Development. The development of the kidneys, and also that of the suprarenal cap- 

 sules will be described later with that of the genito-urinary organs. 



The Urine. This is a complex and somewhat variable fluid, containing in 

 solution animal substances characterised by having a large amount of nitrogen in 

 their composition, and derived, it would seem, from the waste of the tissues ; also 

 saline substances, and adventitious matters which have been introduced into the 

 blood. The average quantity secreted daily is from 30 to 40 fluid ounces. Its specific 

 gravity varies in health from 1-015 to T030, the average standard being T020. It is 

 slightly acid in its reaction, and contains some mucus and epithelium. A thousand 

 parts of ordinary urine usually contain 933 parts of water, and 67 of solid matter. 

 The researches of Bowman upon the structure of the kidney in man and animals, 

 render it probable that the solid urinary constituents are secreted by the tubuli, and 

 that the watery part of the urine simply transudes through the vessels of the glomeruli. 



The following analysis of the solid contents of the urine is from Lehmann, but it 



