514 PASSAGE OF VARIOUS SUBSTANCES INTO THE URINE. 



the ingestion of milk and meat) , the elastic sarcolemma-like substance of the 

 membrana propria of the urinary tubules, and the tissue-elements of the vessels 

 and their unstriated muscles, the kidneys contain leucin, xanthin, hypoxanthin, 

 kreatin, taurin, inosite, cystin (the last is present in no other tissue) ; and of these, 

 the majority pass into the urine either not at all or only in small amount. The 

 presence of these substances indicates, probably, active metabolism in the kidneys; 

 and this is suggested also by the great vessels of the kidney. During the secretion 

 of the kidneys, the blood of the renal vein is said to become bright red, and to 

 be deprived of its fibrin. If alkaline blood-serum be filtered through a layer of 

 nucleo-albumin or lecithin-albumin, an acid filtrate passes through. Liebermann 

 explains in a similar manner the development of acid urine on passing blood- 

 plasma through the renal epithelium containing lecithin-albumin. 



THE PASSAGE OF VARIOUS SUBSTANCES INTO THE URINE. 



The following substances pass unchanged into the urine: Alkaline sulphates, 

 borates, silicates, nitrates, carbonates; alkaline chlorids, bromids, and iodids; 

 potassium sulphocyanate, potassium ferrocyanid; salts of the biliary acids; urea, 

 kreatinin; cumaric, oxalic, camphoric, pyrogallic, sebacylic acids; further, many 

 alkaloids, as, for instance, morphin, strychnin, curarin, quinin, caffein; among the 

 pigments, sodium sulphindigotate, carmine, gamboge, madder, logwood, the color- 

 ing-matter of huckleberries, mulberries, cherries, rhubarb; further, santonin; and, 

 finally, the salts of gold, silver, mercury, arsenic, bismuth, antimony, iron (but 

 no lead) , which, however, pass in largest amount into the bile and into the feces. 



Inorganic acids appear in human beings and carnivora as neutral ammo- 

 nium-salts; in herbivora, as neutral alkaline salts. 



Certain substances that generally undergo decomposition, even when they 

 gain entrance into the blood in small amounts, pass in part into the urine when 

 they accumulate in the blood in considerable amount, because they are not com- 

 pletely decomposed, such as sugar, hemoglobin, egg- albumin, alkaline salts of the 

 vegetable acids, alcohol, chloroform. 



Many substances appear in the urine as oxidation-products: moderate 

 amounts of alkaline salts of the vegetable acids as alkaline carbonates; uric acid 

 in part as allantoin; sodium sulphite acid and hyposulphite in part as sodium 

 sulphate; potassium sulphid as potassium sulphate. Many oxids appear as sub- 

 oxids, benzol as phenol. 



Those bodies, such as glycerin and the resins, that are completely con- 

 sumed, exhibit no special derivatives in the urine. 



Some substances undergo synthesis with metabolic products, and appear 

 in the urine as conjugated combinations. In this category belongs the develop- 

 ment of hippuric acid by conjugation, the formation of the conjugate sulphates, 

 as well as the formation of urea by synthesis from carbamic acid and ammonia. 

 After administration of camphor, or of chloral and butyl-chloral, a conjugated 

 combination with glycuronic acid, an acid closely allied to sugar, appears in the 

 urine. Taurin and sarcosin undergo conjugation with sulphamic or carbamic acid. 

 Phenyl bromid, when administered, enters into conjugation with mercapturic acid, 

 a body allied to cystin. 



Tannic acid, C 14 H 10 O 9 , takes up water, and is thus decomposed by hydro- 

 lysis into two molecules of gallic acid 2C 7 H 6 O 5 . 



Potassium iodate and bromate are reduced to potassium iodid and bromid; 

 malic acid, C 4 H 6 O 5 , in part to succinic acid, C 4 H 6 O 4 ; indigo-blue, C 16 Hi N 2 O 2 , 

 takes up hydrogen to form indigo-white, C 16 H 12 N 2 O 2 . 



Finally, many substances do not pass into the urine at all, such as serum- 

 albumin, oils, insoluble metallic salts, and metals. 



INFLUENCE OF THE NERVES UPON THE SECRETION OF THE 



KIDNEYS. 



As yet, only the influence of the vasomotor nerves upon the ni- 

 tration of the urine from the renal vessels is known, and these nerves 

 appear to be derived from both halves of the spinal cord for each kidney. 

 In general, it should be borne in mind that dilatation of the branches of 



