580 



Prof. T. G. Brodie. 



by the injection of any diuretic which causes a free flow of water, the 

 differences between both glomeruli and convoluted tubules are of the most 

 striking character. These differences are illustrated in figs. 1 and 2, 

 which show the changes in the cortex Under a low magnification. The 

 important points are the following : — In an active kidney the glomeruli are 

 always separated from the capsules, and usually there is a considerable 

 accumulation of fluid in this position. The capsule is always rounded, 

 whereas in the resting kidney the capsule lies in contact with the glomerulus, 

 and the whole structure is usually irregularly polyhedral in shape. In an 

 active kidney, in contradistinction to the resting, the individual loops of the 

 glomerulus are frequently separated from one another and stand out clearly. 

 The glomerulus also has a very characteristic vacuolated appearance, due, we 

 think, to dilated capillaries, from which the red blood corpuscles have in 

 some way or other been removed or destroyed, possibly post mortem. 

 "When examining two such kidneys under a low power of magnification the 

 contrast is most striking. In the resting kidney the glomeruli are far from 

 conspicuous, and have to be sought for. In the active kidney, on the other 

 hand, they stand out at once as the most conspicuous objects in the field of 

 view. 



The changes in the tubules are just as striking. Whereas a resting proximal 

 convoluted tubule possesses no lumen, one in activity has a large lumen. This 

 is true both of the proximal and the distal tubules. Moreover, in the resting 

 kidney the tubules are very much twisted on themselves and form very 

 complicated foldings, whilst in the active kidney the appearances indicate 

 that the tubule is as far as possible straightened out. All these several points 

 prove quite clearly that the tubules have been subjected to some high fluid 

 pressure from within. 



The changes accompanying activity are strikingly emphasised when we 

 measure the diameters of these several structures. In the case of the 

 glomeruli and capsules, in addition to measurements in diameters at right 

 angles to one another, approximate calculations of their volumes were also 

 made. 



In one experiment which we may take as typical we obtained the following 

 results : — 



Besting. After activity. 



Volume of capsule 83* 220 



glomerulus 80 111 



„ fluid in capsule 3 109 



* These figures can be converted into cubic millimetres by multiplying them 

 by 4-2 x 10- 6 . 



