420 Dr. Brunton and Mr. H. Power on Digitalis. [June 18, 



X. " On the Diuretic Action of Digitalis" By T. LAUDER 

 BRUNTON, M.D., D.Sc., and HENRY POWER, M.B., F.R.C.S. 

 Communicated by Dr. SANDERSON, F.R.S. Received June 1, 

 1874. 



It has been shown, by Max Herrmann and Ludwig, that the rapidity of 

 the urinary secretion depends on the difference in pressure between the 

 blood in the renal gloineruli and the urine in the urinary tubules. 



At present, it is generally assumed that the diuretic action of Digitalis 

 is not caused by any specific influence of the drug upon the kidney, but 

 is due exclusively to its power of increasing the blood-pressure in the 

 arterial system. 



The results of some experiments made by us nearly a year ago show 

 that this is not the fact. On injecting a considerable dose of digitalin 

 (1-2 centigrammes) into the veins of an etherized dag, we have observed 

 that the secretion of urine \vas either great! y diminished or ceased alto- 

 gether, while the Wood-pressure rose, occasionally to a considerable 

 extent. After some time the blood-pressure again fell : and in some of 

 the experiments the secretion of urine recommenced at the instant the 

 fall began. In other instances it did not recommence till the blood- 

 pressure had sunk below the normal. Occasionally the secretion did not 

 flow with its original r pidity, but in others it was poured forth 

 copiously, even although the blood-pressure had sunk considerably below 

 the normal. 



If Digitalis acted as a diuretic only by raising the blood-pressure, the 

 flow of urine should have been greatly increased immediately after the 

 injection, and should have diminished with the fall of arterial tension. 

 Instead of this the secretion was least when the blood-pressure was 

 highest, and most copious when the tension had fallen below the normal. 



The explanation we would offer of these phenomena is, that Digitalis 

 probably stimulates the vaso-motor nerves generally, but affects those of 

 the kidney more powerfully than those of o L her parts of the body. Thus, 

 it causes a moderate contraction of the systemic vessels, and raises the 

 blood-pressure in them, but, at the same time, produces excessive contrac- 

 tion of the renal vessels, so as to stop the circulation in the kidneys and 

 arrest the secretion of urine. 



As the action of the drug on the systemic vessels passes off they relax, 

 and the blood-pressure falls ; but the renal arteries probably dilate more 

 quickly and to a greater extent than the others. The pressure of blood 

 in the glomeruli may thus be increased above that normally present in 

 them, although the tension in the arterial system generally may have 

 fallen below the normal. 



Additional evidence in favour of this explanation is afforded by the fact 

 that the urine collected after the reestablishment of secretion contains 

 albumen, just as Herrmann found it to do after mechanical arrest of the 

 circulation through the renal arteries. 



