426 FORMATION OF URIC ACID. 



Uric Acid is formed Outside the Kidneys. 1. Birds' blood normally contains uric acid 

 (Afeissncr). [The liver of the pigeon contains 6 to 14 times as much uric acid as the blood.] 

 Ligature of the meters or renal blood-vessels (Pawlinoff), or gradual destruction of the renal 

 secretory parenchyma by the subcutaneous injection of neutral potassium chromate (Ebsteiri), is 

 followed by the deposition of uric acid in the joints and tissues, and it may even form a white 

 incrustation on the serous membranes. The brain remains free {Zalcsky, Oppler). Acid urates 

 of ammonia, soda, ami magnesia are also similarly deposited. Extirpation of a snake's kidneys 

 gives the same result, but to a less degree. 



[Minkowski found that, after excluding the liver from the circulation, lactic acid took the 

 place of uric acid in the urine (p. 425). Some uric acid still appears in the urine, which cannot 

 be derived from the small amount in the blood, so that, according to v. Schroeder, there are 

 perhaps other foci of formation of uric acid.] 



[The latter experiment points to the formation of uric acid in the liver in birds, 

 and this is supposed to be strengthened by the appearance of the deposition of urates 

 in the urine in certain disorders of digestion.] Von Schroeder and Colasanti, how- 

 ever, as the result of their experiments upon snakes, come to the conclusion that 

 there is no special organ concerned in the formation of uric acid. 



Hippuric acid is partly formed iu the kidney, for the blood of herbivora does not contain a 

 trace of it {Mcissncr and Shcpard). In rabbits, perhaps it is formed synthetically, in other 

 tissues as well as in the kidney. If blood containing sodic benzoate and glycin be passed 

 through the blood-vessels of a fresh kidney, hippuric acid is formed (260) (Bungc, Schmiedeberg, 

 Koihs). [The other evidence is given in 260.] 



Kreatinin has intimate relations to kreatin of muscle, but where it is formed is not known. 

 If phenol and pyrokatechin are digested along with fresh renal substance, a compound of 

 sulphuric acid similar to that occurring in urine is formed ( 262). The latter substance, 

 however, is also formed by similarly digesting liver, pancreas, and muscle. It is concluded 

 from these experiments that these substances are formed in the body within the kidneys and 

 the other organs mentioned {Koch?). 



Chemistry of the Kidney. The kidneys contain a very large amount of water. Besides 

 serum-albumin, globulin, albumin soluble in sodium carbonate (Gotticalt), gelatin-yielding 

 substances, fat in the epithelium, elastic substance derived from the membrana propria of the 

 tubules, the kidneys contain leucin, xanthin, hypoxanthin, kreatin, taurin, inosit, cystin (the 

 last in no other tissue), but only in very small amount. The occurrence of these substances 

 l>oints to a lively metabolism in the kidneys, which is also proved by the liberal supply of blood 

 they receive. 



Blood-Vessels. The kidneys receive a very large supply of blood, and during 

 secretion the blood of the renal vein is bright red. [In the dog, the diameter of 

 the renal artery may be diminished to *5 mm. without the amount of blood flowing 

 through the kidney being thereby greatly interfered with. Hence, within wide 

 limits, the amount of blood is independent of the size of the arterial lumen, and is 

 therefore dependent on the blood-pressure in the aorta, and the resistance to the 

 blood-current within and beyond the kidney {Heidenhain).] 



The reaction of the kidneys is acid, even in those animals whose urine is alkaline. Perhaps 

 this fact is connected with the retention of the albumin in the vessels. 



275. PASSAGE OF VARIOUS SUBSTANCES INTO THE URINE. 1. The following 

 substances pass unchanged into the urine : Sulphate, borate, silicate, nitrate, and carbonate 

 of the alkalies ; alkaline chlorides, bromides, iodides ; potassium sulphocyanide and ferro- 

 cyanide ; bile salts, urea, kreatinin ; cumaric, oxalic, camphoric, pyrogallic, and carbolic acids. 

 Many alkaloids, e.g., morphia, strychnia, curara, quinine, caffein ; pigments, sulphindigotate 

 of soda, carmine, madder, logwood, colouring matter of cranberries, cherries, rhubarb ; santonin ; 

 lastly, salts of gold, silver, mercury, antimony, arsenic, bismuth, iron (but not lead), although 

 the greatest part of these is excreted by the bile and the faeces. 



2. Inorganic acids reappear in man and carnivora as neutral salts of ammonia, in herbivora, 

 as neutral salts of the alkalies. 



3. Certain substances which, when injected in small amount, seem to be decomposed in the 

 blood, pass in part into the mine, when they occur in such large amount in the blood that 

 they cannot be completely decomposed sugar, hfemoglobin, egg-albumin, alkaline salts of the 

 vegetable acids, alcohol, chloroform. 



4. Many substances appear in an oxidised form in the urine moderate quantities of 

 organic alkaline salts as alkaline carbonates (Wohler), uric acid in part as allantoin 

 (Salkmcski), sulphides and sulphites of soda, in part as sodium sulphate, potassium sulphide as 

 potassium sulphate, some oxyduls as oxides, benzol as phenol (Naumyn and Schulzeri). 



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