RENAL EFFICIENCY AND BLOOD-PRESSURE 161 



to a stimulating influence on the vasomotor centre resulting from a defective 

 blood-supply to that centre. The remarkable variability of the pressure from 

 day to day or hour to hour in some high-pressure cases has to be kept in mind 

 in relation to such a view. 



It is obviously possible that with regard to other vital organs, as in the case 

 of the brain, there may be vascular adjustments of a compensatory character 

 involving a rise of aortic pressure. 



In the case of the kidney a rise of general blood-pressure might have 

 a compensatory value in aiding the excretion of concentrated urine, salts, 

 abnormal substances, or excess of acid or other waste products ; or, again, 

 when the materials to be excreted are not abnormal or excessive in amount, but 

 the functioning of the organ is defective from structural change or other causes. 

 The improvement might be associated with increase in the flow of water or 

 determined in other ways. 



Bier (2) first suggested that hypertension with the arteriosclerotic or athero- 

 sclerotic kidney is best regarded as a compensatory efibrt of the organism, to be 

 interfered with only when danger threatens either of cardiac failure or of cerebral 

 haemorrhage. According to this view, by diminishing hypertension, a danger 

 more or less imminent would be replaced by the certain danger derived from an 

 upset of the kidney efficiency, maintained only at an efficient level by the raised 

 blood -pressure. 



Relations of Blood-pressures and Renal Efficiency, 



The existing data bearing on the frequent coexistence of high blood-pressures 

 and defective kidney efficiency do not afford grounds for determining the relations 

 between the former and the latter. Examination of the relations between the 

 heights of the blood-pressures and the existence and degree of ascertained defects 

 in urinary excretion (urea, &c.) as studied in different individuals is obviously 

 inadequate, since the degree of kidney damage which may be present in the 

 different subjects constitutes a factor of unknown value. This factor may 

 obviously determine various relations between the levels of blood-pressures 

 present and the degrees of defect in urinary excretion. If it is assumed for the 

 moment that high blood-pressure (as many believe) can favour kidney efficiency, 

 the fact remains that there might be very different degrees of defective excretion 

 in presence of equally high blood-pressures, and, on the other hand, that excretion 

 might be relatively good in association with comparatively low blood-pressures — 

 the existence of varying (unknown) amounts of kidney damage constituting the 

 deciding factor in the different subjects examined. 



To test the relationship of high blood-pressures and renal efficiency it 

 is clearly necessary to make observations on the same individual in whom, with 

 given kidney conditions, lowering of the blood-pressure is purposely induced in 

 order to ascertain what alteration, if any, in renal efficiency occurs in associa- 

 tion with the alteration in the blood-pressure, the response of the kidneys 



F f 2 



