178 QUARTERLY JOURNAL OF MEDICINE 



8. The excretion of urea was not interfered with by a large fall of blood- 

 pressure in a high-pressure case by venesection. 



9. The virtual maintenance of the total excretion of urea during the period 

 of lowered blood-pressure in cases of hyperpiesia indicates that the mechanism of 

 hyperpiesis is not to be regarded as compensatory, at least so far as the excretion 

 of urea and non-protein nitrogen is concerned — a conclusion in accord with the 

 results of some clinical observations as regards phenolsulphonephthalein excretion 

 reported by Gruber (4), and guanidine excretion by Major (7). 



10. No definite relationship is observable between the amount of urea in the 

 blood and the height of the blood-pressure. 



11. Nitrites should not be administered either prior to or during the 

 application of MacLean's test. 



12. Apart from the application of the urea concentration test, useful evidence 

 as to the urea-concentrating power of the kidney may often be obtained from the 

 examination of individual specimens of urine over the twenty-four hours, since in 

 some of such specimens there may be a percentage of urea as high as, or even higher 

 than is shown by MacLean's test. 



I am indebted to Professor J. A. MacWilliam for much kindly help and 

 criticism, and to Dr. W. Brander, Medical Superintendent, Hackney Infirmary, 

 Loudon, for facilities for examining cases and for carrying out part of the necessary 

 laboratory work. 



My thanks are also due to the Medical Research Council for a grant in aid of 

 the expenses of the above investigation. 



REFERENCES. 



1. Anrep, G. V., and Starling, E. H., Proc. Roy.Soc, Lond., 1925, B., xcvii. 463. 



2. Bier, A., Miinch. med. Woch., 1900, xlvii. 527. 



3. Cushny, A. R., Pharmacology and Therapeutics, 8th edit., Lond., 1924, 403. 



4. Gruber, C. M., &c., Arch. Int. Med., Chicago, 1925, xxxvi. 366. 



5. Herringham, W. P., Kidney Diseases, Lond., 1912, 219. 



6. Hill, L., Schafet^s Textbook of Physiol., Lond., 1900, ii. 136. 



7. James, A. A., Laughton, N. B., and Macallum, A. B., Science, N. York, Ixii. 1 81. 



8. Macdonald, W. J., Ptvc. Soc.Exper. Biol, and Med., N. York, 1925, xxii. 483. 



9. MacLean, H., Renal Diseases, Lond., 1921, 53. 



10. MacLean, H., ibid., Lond., 1921, 44. 



11. MacLean, H., ibid., Lond., 1921, 48. 



12. MacWilliam, J. A., and Melvin, G. 3., Heart, Lond., 1913-14, v. 153 ; Brit. Med.Joum., 

 Lond., 1914, 1. 693. 



13. Major, R. H. Joum. Amer. Med. Assoc, Chicago, 1925, Ixxxv. 251. 



14. Major, R. H., Bull. Johns Hopkins Hasp., Baltimore, 1925, xxxvi. 357-60. 



15. Major, R. H., and Stephenson, W., ibid., Baltimore, 1924, xxxv. 140 and 186. 



16. Mason, E. C, Joum. Lab. and Clin. Med., St. Louis, 1923-4, ix. 529. 



17. Starling, E. H., Brit. Med. Joum., Lond,, 1925, ii. 196. 



