164 THE ARMY FOR HOME DEFENCE 



into the cell to make up the deficit. The experiments of Milroy 

 and Donnegan, already referred to, contain a series demonstrating 

 the passing of NaCl from a watery solution to one containing a 

 globulin. 



Cushny's obstructed ureter experiment referred to above may 

 be interpreted in this light. Assuming, as he does, that the fluids 

 coming from both capsules are identical in both kidneys, then on 

 the obstructed side there is a fluid in prolonged contact with the 

 tubular epithelium, while on the other this fluid passes away more 

 or less rapidly. Take for granted, for the sake of a standard, 

 that the freely passed urine remains unaltered, that is, it is equal 

 to the glomerular filtrate on the obstructed side e.g. 24 gms. 

 water, 0-08 gms. NaCl and 0-11 gms. Na 2 SO 4 . Sodium chloride 

 is more diffusible than sulphate and readily penetrates cells, there- 

 fore the positive tension of NaCl in the tubule will cause some 

 NaCl and water to enter the lining cells and so into the blood 

 stream. The sulphate, not being so diffusible, will not so enter 

 the cell. Thus the result would be a concentration of the urine 

 with a decrease in chloride, i.e. with sulphate steady ; chloride 

 would drop to a quarter =0-02 and water to a half =12 gms. 

 But no great energy need be expended here, only sufficient to 

 evaporate urine to half its bulk. The water and salt so secreted 

 into the blood stream would cause a further diuresis and so on. 

 On the other hypothesis, viz. that the sulphate is to a great extent 

 secreted by the tubule epithelium into the lumen, this difficulty 

 does not to the same extent arise. 



In short, two factors may come into play in the secretion of 

 urine, (a) the adjustment of the cell to alterations in its environ- 

 ment, and (b) a mechanical dialysis of water and crystalloids in 

 solution through the capsule under sufficient pressure to wash 

 the actively secreted material through the collecting tubule and 

 on towards the pelvis of the kidney. 



Other Glands of Elimination. 



Of the physics of the other detoxifying glands, little or nothing 

 is known. The largest of these is the liver, but beyond the 

 isolation of enzymes, the physico-chemical mechanism has not 

 been to any great extent investigated. 



The spleen is the burying-place of dead erythrocytes. It is a 

 modified lymph gland where the blood comes into intimate 

 contact with the spleen cells or " pulp." In structure it is a 

 spongework of fibrous tissue, in a capsule of the same material 



