RENAL EFFICIENCY AND BLOOD-PRESSURE 177 



not necessarily the maximum for the kidneys of that individual, since some of the 

 individual specimens of urine obtained (apart from administration of urea) 

 throughout the twenty-four hours contain in many cases as high percentages of 

 urea as those obtained in the test specimens, sometimes even higher, as shown in 

 Table VI, Cases 24, 26, 27. It would appear, therefore, that useful guidance 

 to the power of the kidney to concentrate urea can sometimes be obtained 

 by ascertaining the percentages of urea in individual specimens of urine passed at 

 different periods throughout the twenty-four hours. 



Conclusions. 



1. In the healthy subjects the diuresis which usually follows the administra- 

 tion of 15 grm. urea may or may not be cut down by drugs of the nitrite series 

 in the doses stated, and the power of the kidney under the above conditions to 

 concentrate urea is not impaired. The blood urea and non-protein nitrogen are 

 not increased. 



2. In high-pressure cases the diuresis which usually follows the administra- 

 tion of 15 grm. urea is usually cut down by drugs of the nitrite series in the doses 

 stated. 



3. The total excretion of urea following the administration of 15 grm. urea 

 is usually not diminished by the administration of nitrites in doses sufficient 

 to cause a considerable lowering of the high blood-pressures present (falls of 

 20-60 mm.). 



4. The power of the kidney to concentrate urea after the exhibition of 

 15 grm. urea is not impaired, inasmuch as urine of higher urea concentration 

 is still excreted during the period of lowered pressure, e. g. 2-8, 3'0, 3-5, as 

 compared with 1'7, 2*2, 2-0 respectively, when the test is applied before the 

 lowering of the pressure. It remains to be seen whether (apart from the evidence 

 afforded by the unimpaired total urea excretion) high urea concentration values, 

 e.g. 3-5, 3-8, during the period of lowered pressure are significant with regard to 

 reduction of pressure being warrantable, so far as the kidney is concerned. 



5. If vasodilator drugs are given in pharmacopoeial doses as distinguished 

 from the larger doses referred to above, the functions of the kidney as regards the 

 excretion of water, the excretion of urea, and the power to concentrate urea 

 are not diminished. 



6. The urea and non-protein nitrogen content of the blood is not increased 

 by the administration of vasodilator drugs over periods ranging from twenty-four 

 hours to more than one week. The increased urea concentration in the urine is 

 evidently not dependent on an increased percentage in the blood. 



7. If the larger doses are maintained over a longer period, symptoms of 

 intolerance to the drug supervene long before the stage of suppression of urine. 

 Symptoms of intolerance may arise in different cases where the power of the 

 kidney to concentrate urea is either (1) above 2 per cent., or (2) well below 

 2 per cent. 



a g 2 



