582 



Prof. T. G. Brodie. 



This is fairly typical of the results obtained in all our experiments. We 

 found it to be practically a universal rule that the external diameter of the 

 proximal convoluted tubule remained unaltered, or showed but a slight 

 increase or decrease. The marked change during activity is the production 

 of a big lumen within the proximal tubule. The idea given by an examination 

 of the sections is that the loops of the convoluted tubule have been opened 

 out and stretched in length. They are in nearly all instances circular in 

 outline, and invariably, as just stated, there is a very wide lumon. The distal 

 convoluted tubule in contradistinction is nearly always increased in diameter 

 in the active state, and the lumen greatly increased, often doubled, although 

 this tubule has invariably a rather large lumen even in the resting kidney. 



We have not yet carried out a sufficient number of measurements of the 

 remaining portions of the tubule to warrant us making any decided statement 

 as to the changes they undergo. It is clear that the limbs of the loop of 

 Henle are both distended, and often the collecting tubules show very distinct 

 expansion. 



The next modification in our experiments consisted in comparing the two 

 kidneys after active diuresis, one kidney having been previously stripped of 

 its Capsule. 



The kidney is very characteristically enclosed in a strong and 

 practically inextensible Capsule*, and my view of the meaning of 

 the glomerulus offers an explanation of that fact. As fluid is 

 secreted into Bowman's capsule by the epithelium covering the 

 glomerular loops, and possibly also by the epithelium of the capsule, 

 the blood -pressure acting within the glomerular loops is transmitted directly 

 to that fluid and through it to the wall of Bowman's capsule. This latter, 

 as we have seen, is extensible and might be ruptured if the distension 

 were carried too far. Again, fluid is at once forced into the convoluted 

 tubule, and that also might be ruptured if overdistended. To prevent any 

 dangerous overdistension the whole of the structures are enclosed in a firm 

 Capsule. That this distension does take place on activity is amply proved in 

 a variety of ways. Firstly, as shown above, the histological appearances 

 demonstrate it. Secondly, if in an experiment we excise one kidney at the 

 commencement, then excite diuresis, and at its height ligature the pedicle of 

 the other kidney to prevent escape of urine from the tubules, and we then 

 weigh the two kidneys, the latter often shows an increase in weight amount- 

 ing to about 30 per cent. This increase in weight is not due to blood, for 

 on excision the blood escapes more readily from such a kidney than from a 



* In order to avoid confusion between the Capsule of the kidney and Bowman's 

 capsule, I will when referring to the former distinguish it by a capital. 



