DIURESIS 161 



Next, one wants to consider what cells the sulphate stimulates. 

 Cushny caused one kidney to secrete against a pressure of 30 mm. 

 Hg., leaving the other kidney free. During the height of a 

 NaCl+Na 2 SO 4 diuresis he found that for equal weights of urine 

 the obstructed kidney produced a fluid containing less chloride 

 and more sulphate than the kidney with unobstructed ureter. 

 The result of one experiment is appended. 



Urine Gms. Cl. Gms. SO 4 Gms. 



() Unobstructed side - 24 0-081 0-108 



(6) Obstructed side 8 0-014 067 



He supposed that the filtrate from Bowman's capsule must be 

 of identical composition in both kidneys, as both had the same 

 blood supply. Therefore, some change must have taken place 

 during the passage along the tubules. In one case (obstruction) 

 the fluid remained in contact with the lining cells for a prolonged 

 period, while on the other side free passage was allowed. Either 

 sulphate must have been added to the fluid during its stay in the 

 tubule or chloride and water absorbed. The two main modern 

 theories of renal action differ on this point. The experiment is 

 quoted at this stage to demonstrate that it is probable that 

 sulphate stimulates the cells lining the tubule, and that their 

 activity entails the consumption of oxygen and the expenditure 

 of energy. 



It is very difficult to get reliable experimental results from the 

 kidney. Its nature, blood supply and position do not lend them- 

 selves to surgical interference, and the student ought to be keenly 

 critical of results which are produced under uncontrolled abnormal 

 conditions. Some facts, however, are obtainable and may be 

 detailed here shortly. 



1. Function. No one doubts that the kidney as a cell-com- 

 munity has specialised in excretion. Every cell in the body has 

 the power of eliminating waste products. Most of these substances 

 find their way into the blood and those that are non-volatile are 

 voided by the kidney cells. 



2. Structure. 



The functioning parts seem to be structurally, two, (a) the 

 capsules, and (b) the tubules. Each capsule is lined by flattened 

 pavement cells supported by a delicate basement membrane. 

 The tubules are formed of columnar cells containing rows of 

 granules running radially towards the lumen and becoming finer 

 as they reach the striated border of the cell-lumen interface. 



