THE CELLS OF BOWMAN'S CAPSULE 713 



chloride can stop the glycosuria of a saline diuresis without affect- 

 ing the diuresis can, on Lud wig's view, not be explained by any 

 action on the glomerulus, but must be due to the same ion pro- 

 ducing a selective influence on the absorbent power of the tubule 

 cells. Such a thing is conceivable. For, while it has been found 

 generally that anions increase and kations retard the activity 

 of various cells and ferments, it has also been found that the same 

 ion may so influence the properties of a given cell as, for instance, 

 to give it a selective permeability which it did not previously 



The Properties of the Cells of Bowman's Capsule. The 



bare possibility of Lud wig's view depends upon the properties of 

 this membrane ; for it must under all conditions in which any 

 filtration takes place through it at all be equally permeable to all 

 crystalloids. The difficulties of determining the permeability of 

 this membrane are obvious ; it is impossible either to experiment 

 with it directly or to obtain the glomerular filtrate as it leaves 

 the membrane. There is no known artificial membrane which 

 has properties exactly similar to those which on Lud wig's view 

 the glomerular epithelium must possess. For we know of no 

 membrane for which the concentration of crystalloids in the filtrate 

 is that of the original solution. Important analogies have been 

 drawn from a study of gelatine membranes ; but these membranes 

 are equally impermeable to the blood proteids and egg albumin, 

 while the cells of Bowman's capsule keep back the blood proteids 

 and let through egg albumin. We know nothing about what 

 determines the permeability of dead membranes for different 

 substances in solution ; permeability may be a chemical pheno- 

 menon, a physical one, or both. We know nothing, of course, 

 about the permeability of living cells ; whether it has a physical 

 and chemical basis, or depends upon some other property of the 

 bioplasm which is associated with its living activity and must be 

 called vital, we do not know. 



There can be no doubt that the glomeruli do produce at least 

 the major part of the water of the urine ; Nussbaum's experi- 

 ments of ligaturing the renal arteries in the frog show this. 

 But when we look for other experiments to indicate the role of the 

 glomerulus in the production of urine, we find that there are only 

 very few which give us the slightest hint of the properties of the 

 glomerular epithelium. Adami thought that he had definitely 



