350 HERMAN O. MOSENTHAL 



may occur if the blood becomes very inspissated, as in cholera; cardiac 

 decompensation results in retention of water and chlorids ; a dilute blood, 

 as in the anemias, brings about a low urinary concentration ; cystitis and 

 pyelitis may do the same ; obstruction of the ureters, or urethra by stone, 

 carcinoma, hypertrophied prostate or stricture at times cause marked 

 renal insufficiency, etc. It is obvious, from what has been briefly noted, 

 that the term renal function, in the clinical sense, is not synonymous with 

 kidney efficiency, but. includes all the processes in the body that influence 

 the kind and amount of urine that passes the urethra. The physician, 

 dealing with Bright's disease, must necessarily bear this definition, and 

 its significance, in mind when interpreting tests for renal function. 



Tests for renal function may be considered as falling into three groups : 



1. Tests for renal function "as a whole." 



2. Tests that attempt to determine the anatomical location of the im- 

 pairment of efficiency, tubules, glomeruli, or blood vessels. 



3. Tests whose purpose it is to ascertain the power of the kidneys 

 to eliminate one or more of the substances such as urea, sodium chlorid, 

 creatinin, uric acid, water, etc., which are ordinarily excreted in the urine. 



Such a classification of tests for renal function is very useful. It fur- 

 nishes a synopsis of the development of this branch of medical science 

 and in addition serves to point out the deficiencies in the present day 

 knowledge of the action of the kidneys under physiological and pathological 

 conditions. The earliest successes in obtaining an idea of renal efficiency 

 was by tests which indicated the ability of the kidney to functionate "as 

 a whole." This phrase was advocated by the observers who favored these 

 procedures. It is very expressive inasmuch as the substances used 

 principally dyestuffs do not parallel any of the known excretory sub- 

 stances in the urine absolutely, and are not, as far as generally acknowl- 

 edged, eliminated by a definite portion of the renal structure. The phenol- 

 sulphonephthalein test is the one most widely used, and is the only one 

 of this group which will be considered in detail ; it has been of great serv- 

 ice in promoting the knowledge of nephritis and is still of supreme im- 

 portance to the physician with limited laboratory facilities; it has, 

 however, been largely replaced by procedures that give information regard- 

 ing the specific functions of the kidney. It has gradually come to be ap- 

 preciated that such specific tests give the greatest amount of informa- 

 tion and that renal efficiency is hardly ever curtailed as a whole, but 

 to a greater extent in certain directions than in others. To be oriented 

 on these points tends to a more accurate functional diagnosis and better 

 therapy. 



The Phthalein Test. "Phenolsulphonephthalein, which was first de- 

 scribed by Remsen, is a bright red crystalline powder, somewhat soluble 

 in water and alcohol and readily soluble in the presence of alkalies. The 

 drug, as determined by Abel and Rowntree, is non-toxic, non-irritant 



