MECHANISM OF RENAL SECRETION 47 



lumen. In some cases there was rather distinct Prussian blue staining 

 of the intercellular membranes. 



Ten minutes {K39). Adult female rabbit. Weight = 2350 grams. 

 Injected 0.43 gram green ferric ammonium citrate intravenously. 

 Animal killed ten minutes after the injection. Kidneys fixed in: 

 95 per cent alcohol. 

 Zenker's fluid. 

 The urine in the bladder at death contained iron. 

 Histological findings : In this experiment iron was present in consid- 

 erable, amounts in the blood-vessels. This was markedly noticeable in 

 the glomerular tufts. There was very little iron present in the con- 

 voluted tubules and this was located primarily in the cytoplasm between 

 the free border at the lumen and the nucleus. The lumina of the col- 

 lecting tubules of the medulla and the pelvis of the ureter also con- 

 tained Prussian blue in rather considerable amounts. 



Twelve minutes {KS4)- Adult male rabbit. Weight — 1600 grams. 

 Injected 0.3 gram green ferric ammonium citrate plus 0.3 gram sodium 

 ferrocyanide intravenously. Animal killed twelve minutes later. 

 Kidneys fixed in: 



95 per cent alcohol. 

 5 per cent trichloracetic acid. 

 Zenker's fluid. 

 The urine in the bladder at death contained iron. 

 Histological findings: Nearly all the iron in the preparations of this 

 experiment was in the lumen of the collecting tubules of the medulla 

 and in the medullary rays. Iron was also present in the lumen and 

 cells of the convoluted tubules. In the cell the iron was scattered in 

 the cytoplasm in the half of the cell toward the lumen of the tubule. 

 Fifteen minutes {K25). Adult male rabbit. Weight = 1970 grams. 

 Injected 0.4 gram green ferric ammonium citrate intravenously. Ani- 

 mal killed fifteen minutes later. Kidneys fixed in: 

 Absolute alcohol. 

 Zenker's solution. 

 Urine in the bladder at death contained considerable iron. 

 Histological findings: There was a great deal of iron in the lumen of 

 the collecting tubules. In the cortex the iron was found present in 

 the medullary rays and diffusely in the cells of the convoluted tubules. 

 There was also some Prussian blue in the lumen of the convoluted 

 tubules. 



Twenty minutes {K28). Adult male rabbit. Weight = 2300 

 grams. Injected 0.46 gram green ferric ammonium citrate plus 0.46 

 gram sodium ferrocyanide intravenously. Animal killed twenty 

 minutes later. Kidneys fixed in : 

 95 per cent alcohol. 

 5 per cent trichloracetic acid. 

 4 parts Zenker plus 1 part trichloracetic acid. 

 Plain Zenker's solution. 

 Carnoy's fluid plus trichloracetic acid. 



