A New Conception of the Glomerular Function. 579 



the loop of Henle, i.e. along considerably more than one-half of the whole 

 tubule, and the whole length of the narrowest part of the tubule, the pressure- 

 head required would be enormous, certainly many times greater than the 

 glomerular blood-pressure. We should, therefore, be compelled to ascribe 

 to the cells secreting the water the power of setting up a very high hydro- 

 static pressure, and all the evidence is strongly against any such view. A 

 pressure within Bowman's capsule greater than the blood-pressure would at 

 once lead to the closure of the glomerular loops and arrest of the circulation. 

 This is the main reason why neither the cells of Bowman's capsule, nor these 

 covering the glomerular tufts, nor those of the convoluted tubule, possess the 

 power of setting up a hydrostatic pressure. 



The quantity of energy imparted by the blood to the glomerular secretion 

 is only a small percentage of its total amount. Thus if V be the minute 

 volume of blood flowing through the glomerulus, and v the minute volume of 

 glomerular secretion, then V c.c. of blood enter the glomerular capsule, and 

 V — v c.c. leave it. If p be the pressure-head in the glomerular loops, the 

 pressure energy of the blood entering is Yp, and that of the blood leaving is 

 (V— v)p. The pressure energy communicated to the glomerular secretion is 

 vp, and the ratio of this to the total pressure energy of the blood as it enters 

 is v/Y. In the dog's kidney V may have any value from 200 to 600 c.c, and 

 v from 1 to 2 c.c. at the height of a diuresis. Thus the pressure energy given 

 up by the blood lies somewhere between 1 and 0"16 per cent, of its total 

 pressure energy. 



Histological Evidence. 



In the next instance the test applied was that of microscopical examination 

 of the kidney after varying degrees of activity. If during diuresis fluid is 

 being forced at a considerable pressure from Bowman's capsule down the 

 tubule, evidences of the action of this pressure should be indicated by changes 

 both in the glomerulus and in the tubule. It is very remarkable that 

 throughout the literature the accounts of changes in the glomerulus following 

 activity are so scanty, and many authors state that no changes whatever are 

 to be found {e.g. Lamy and Mayer). Mackenzie and I therefore examined a 

 number of kidneys excised after diuresis had been induced under various 

 conditions, and found that decided changes are produced in the glomerulus 

 and tubule. We further found abundant evidence proving that the tubules 

 have been subjected to a high internal pressure. The full details of these 

 changes are given in a separate paper.* The general results are as follows : — 



On comparing a resting kidney with one that has been thrown into activity 



* Vide p. 593. 



