SECRETION. 459 



Exceptional or Pathological Components. Besides the ordinary 

 constituents of the urine, there may at times be found in it excep- 

 tional ones of pathological significance. 



ALBUMIN. Albumin, and more properly albumin of Uood-serum, 

 is an abnormal component of the urine which has great importance 

 for the physician. Its presence in this secretion gives the clinical 

 condition commonly termed albuminuria. Its presence is due to a 

 great number and variety of causes, a few of which are: (1) tem- 

 porary or lasting increase of pressure of the blood within the renal 

 system, especially hyperaamia from cardiac defect; (2) exanthemata 

 (scarlatina), and febrile diseases in general (pneumonitis, typhus, 

 pyaemia); (3) inflammation and degeneration of the kidneys, as well 

 as disturbances and inflammation of the brain and epilepsy; (4) any 

 substance which acts upon the vascular system of the kidneys, such 

 as diuretics, mercurials, and cantharides. 



The recognition of albumin in the urine requires care, and, above 

 all, it is necessary to remember some of the reactions that occur in 

 the urine. If the urine be acid, the albumin accidentally contained 

 there coagulates at temperatures above 70 C., the coagulation first 

 showing as an opacity upon the surface of the liquid. 



Again, if the urine be alkaline and then subjected to heat, there 

 may result a marked opacity without the presence of albumin, the 

 darkening being caused by precipitation of phosphates. To differ- 

 entiate from phosphates, a few drops of acetic acid are added, which 

 immediately dissolve them. 



Heller's Nitric-acid Test. Albumin is also recognized by means 

 of adding one-fourth of the proper volume of HN0 3 . The reaction, 

 a ring of white precipitate occurring at the junction of the two 

 liquids, is evident when there is much albumin. If, instead, the 

 quantity should be small and the urine concentrated, nitrate of urea 

 will be precipitated, giving an erroneous impression to the observer. 

 If the urine be diluted one-fourth with water, the urea precipitate 

 disappears. 



A method of measuring the quantity of albumin present in urine 

 is easily accomplished by the method devised by Esbach. The essen- 

 tial principle is precipitation of the albumin by means of Esbacfr's 

 reagent, which in 1000 cubic centimeters of water contains 10 grams 

 of picric acid and 20 grams of citric acid. This is performed in a 

 test-tube so graduated that the figures represent grams of dried 

 albumin in a liter of urine. It is essential that the reaction be 





