86 E. J. STIEGLITZ 



portion is at all concerned therewith is not absolutely certain, 

 but if it is, the secretion is minimal. We do not believe that this 

 work has at all proved that there is no resorption of substances 

 along the course of the uriniferous tubule, as postulated by 

 Cushny, but it is clear that it is not the sole function to be 

 ascribed to the tubules. The remarkable localization of function 

 demonstrated in the process of iron secretion and similar specific 

 locahzation of susceptibihty to injurious agents (Aschoff and 

 Suzuki) are facts of extraordinary interest, for they show us that 

 two cells with identical appearance histologically may be endowed 

 with different physiologic properties. Too much stress has 

 been laid in the past upon mere apparent relationships and 

 similarities and the conception of cellular and tissue specificity 

 is a relatively new field, but one of vast importance. To the 

 bacteriologists and serologists, not to the physiologists, belongs 

 the credit for the earliest recognition of its importance. In this 

 connection it is right to mention the illuminating work on chem- 

 ical-tissue specificity done with the Abderhalden reaction (96). 

 We cannot overemphasize the importance of the whole field of 

 investigations dealing with such specificity. 



Iron, probably through its active tendency to dehydrate 

 colloids, produces significant functional changes in the renal 

 cells. Not only is it accumulated, but its presence causes an 

 inhibition of the secretion of further iron, of water, of carbonates, 

 of phenolsulphonephthalein, and of other urinary solutes (as 

 evidenced by the lowered specific gravity). Thus we must 

 consider that excessive iron retention prolonged over a consider- 

 able period must be injurious through preventing the normal 

 elimination of the body's waste products. Therefore, although 

 in the test-tube experiment iron should be an active diuretic, 

 in the body it actually suppresses renal activity because of its 

 conspicuous tendency to become concentrated intracellularly. 

 Such prolonged retention damages the renal cells, and we believe 

 that it is through such gradual, readily controlled and mild 

 poisoning that we will eventually be able to arrive at conclusions 

 regarding the mechanics of 'cloudy swelling.' 



