EXCRETION BY THE KIDNEYS 483 



Various amino-acids are present in solution in the urine in many 

 pathological conditions. Of these the least soluble are leucin and 

 tyrosin, and this is the reason why they are most easily detected. A 

 general reaction for amino-acids is their precipitation as sparingly 

 soluble compounds (/3-naphthalinsulphones) by /3-naphthalinsulpho- 

 chloride in the presence of an alkali (sodium hydroxide). In acute 

 yellow atrophy of the liver leucin and tyrosin have been found in large 

 amounts in the liver itself, as well as in the urine. In phosphorus 

 poisoning these amino-acids, as well as glycocoll, have been detected in 

 the urine, and there is no doubt that other amino-acids, arising from 

 the decomposition of proteins, are also present in such conditions. 



Sugar. In diabetes mellitus, although the .quantity of urine is usually 

 much increased, its specific gravity is above the normal; and this is due 

 chiefly to the presence of sugar (dextrose), which generally amounts 

 to i to 5 per cent., but may in extreme cases reach 10 or even 15 per 

 cent., more than half a kilogramme being sometimes given off in twenty- 

 four hours. 



The name of the tests for dextrose is legion. They are mostly 

 founded on its reducing action in alkaline solution. Hydrated oxide of 

 bismuth (Boettcher), salts of gold, platinum and silver, indigo (Mulder), 

 and a host of other substances, are reduced by dextrose, and may 

 be used to show its presence. The reduction of cupric salts (Trommer), 



Fig. 186. Leucin Crystals. Fig. 187. Tyrosin Crystals. 



fermentation by yeast, and the formation of crystals of phenyl-glueo- 

 sazone are the best established tests. (See Practical Exercises, p. 517.) 



Proteins. Serum-albumin and serum-globulin are the proteins most 

 commonly found in pathological urine. Both are coagulated by heating 

 the urine, slightly acidulated if it is not already acid, or by the addition 

 of strong nitric acid in the cold. Proteoses (albumoses) are also occa- 

 sionally present, e.g., in the disease called ' osteomalacia ' and in con- 

 ditions associated with the formation and especially with the decom- 

 position of pus. They may be recognized by the tests given in the 

 Practical Exercises (p. 517). It is doubtful whether the presence of 

 true peptone has as yet been satisfactorily made out. 



The presence of bile-salts may be shown by Hay's test or Petten- 

 kofer's test (p. 456). 



The pigments of blood and bile may be detected by the characters 

 described in treating of these substances; the spectrum of oxyhaemo- 

 globin, or methaemoglobin, or any of the other]derivatives of haemoglobin, 

 with the formation of haemin crystals, would afford proof of the presence 

 of the former, and Gmelin's test of the latter. The red blood-corpuscles, 

 seen with the microscope, are the most decisive evidence of the presence of 

 blood, as leucocytes in abundance are of the presence of pus. It should 

 be remembered that pus in the urine of women has sometimes no signifi- 

 cance except as showing that there has been an admixture of leucorrheal 

 discharge from the vagina. (See Practical Exercises, pp. 74, 523.) 



