A New Conception of the Glomerular Function. 585 



Lastly, in an experiment in which an obstructed kidney was compared to 

 a decapsulated one we found that the former procedure produced more effect 

 than decapsulation. 



Maximum Ureter Pressure. — Another series of observations which receive 

 a satisfactory explanation is that in which the maximum ureter pressure is 

 measured. According to my theory, fluid should be forced out of the tubules 

 only when the pressure within the ureter lies below the maximum glomerular 

 blood-pressure. This of course assumes that the tubular epithelium in 

 secreting does not set up any appreciable hydrostatic pressure. From this 

 point of view the measurement of the maximum ureter pressure should be a 

 means of determining the intraglomer'ular blood-pressure, always supposing 

 that none of that pressure is taken up by the walls of the glomerular loops. 

 Now the measurements of the maximum ureter pressure fit in perfectly with 

 this conception. In an animal whose aortic blood-pressure is about 120 mm. 

 Hg, the maximum ureter pressure is usually found to be somewhere between 

 80 mm. and 90 mm- Hg, that is, a loss of pressure-head of some 30 to 40 

 mm. Hg occurs between the aorta and the glomerular capillaries. This is 

 distinctly less than is the case for most systemic vessels, and fits in well with 

 our knowledge of the relatively wide and short path of the blood stream from 

 the aorta to the glomerulus. We have only to recall how fast the blood may 

 flow through the kidney to realise that the glomerular capillary pressure 

 during activity must stand at a greater height than the ordinary systemic 

 capillary pressure. 



Let us then return to a general restatement of the whole problem. I 

 have given evidence that the glomerulus, Bowman's capsule and certain parts 

 of the tubules are elastic structures, and that their overdistension is prevented 

 by the general inextensibility of the connective tissue framework and of the 

 Capsule. Consequently as soon as fluid is secreted by the glomerular surface 

 into the capsule, the glomerular capillary pressure comes into play, and some 

 part of that pressure is transmitted through Bowman's capsule to the tubules 

 immediately outside. Then as the secretion continues to accumulate, the 

 kidney expands to fill the Capsule, and the pressure within the Capsule 

 reaches its maximum. Hence we may regard the glomeruli as a number of 

 expanding vascular tufts, lying within a space which cannot expand beyond 

 a certain point, consequently the expansion of the glomeruli expels any fluid 

 free to move outwards. It is as if we were dealing with a sponge work filled 

 with fluid, and enclosed in a capsule which it completely fills. Distributed 

 through the sponge are a number of elastic structures which can be expanded 

 by a fluid pressure acting from within, their expansion necessarily compressing 

 the sponge, i.e. expelling the fluid from between its interstices. This analogy 



