RENAL EFFICIENCY AND BLOOD-PRESSURE 171 



Two factors enter into the determination of the increase in the total urea 

 excreted in cases showing an increase : (a) increased concentration of urea ; 

 (6) increased volume of urine. These factors may operate singly or in com- 

 bination. The increase in the total urea is due to : 



(1) Increased concentration of urea in the urine. 



Cases 4, 9, 12, 20. 



(2) Increased volume. 



C^se 11 (acute nephritis). 



(3) Both factors. 



Cases 6, 7, 18. 



The slight decrease in the total urea in Cases 3, 5, 10, 21, is associated with 

 a great diminution in the volume of urine excreted. 



Two healthy young adults were examined under the same routine observed 

 in the preceding pathological cases. The results are contained in Table IV on 

 pp. 424-5. 



Case 22 showed, under the influence of the vasodilator, increased excretion of 

 urine (33 per cent.), increased total urea (22 per cent.), and slight decrease in the 

 urea concentration percentage of the urine. The increased excretion of urea 

 would thus be accounted for by the increased excretion of urine. On the other hand, 

 Case 23 showed a slight diminution in the amount of urine excreted, no substantial 

 change in the total amount of urea, and no diminution in the urea concentration 

 percentage. The variation in the effects on urinary volume in these two cases is 

 in accordance with Cushny's statement (3) that occasionally a slight increase in 

 the urinary volume may be observed, at other times a decrease. These eflfects are 

 evidently due to the changes in the calibre of the renal vessels. A small quantity 

 may widen them when they are too contracted to allow of the maximal secretion, 

 while on the other hand, if the normal calibre is the optimal, a nitrite may 

 lessen the secretion by lowering the general blood-pressure. When large quantities 

 lower the pressure greatly, they inevitably lead to a lessened secretion or anuria. 



In order to exclude the possibility of a retention of blood urea in the early 

 stages of the administration of the vasodilator drug (leading to the increased 

 percentage of urea in the urine), the blood urea was examined about four hours 

 after the drug had been given in the two normal subjects and in the following 

 group of pathological cases dealt with in Table VI. 



Cases 22 and 28. 



30.10.24. Liq. tnnitrini CX)ij 3-ltourly for 24 hours. 

 Case 22. 



Blood Urea. 

 31.10.24 25 



1.11.24 22 



3.11.24 24 32 10 a.m. 15 grm. Urea after 10 a.m. 



Liq. tnnitrini Q)ij at 3 p.m. and 6 p.m. 

 29 41 7 p.m. 



