54 E. J. STIEGLITZ 



of iron in, the convoluted tubules, was confirmed by the his- 

 tologic study of this experiment. In the material fixed with 

 Zenker's fluid, as control, the malpighian bodies were perfectly 

 normal, but the cells of the convoluted tubules were small, sur- 

 rounding enlarged lumina, and in some places there was desqua- 

 mation. Hyaline casts were found in the collecting tubules of 

 the medulla, but none was noted in the cortex. In the last days 

 of the experiment casts were also noted in the urine. The cells 

 of the convoluted tubules showed a more than normally granu- 

 lar cytoplasm, but the nuclei were apparently normal. With 

 Bensley's aniline-acid fuchsin, methyl green mitochondria stain 

 (50) the sections showed a loss of the mitochondrial content of 

 the cells in the convoluted tubules. 



In the tissue fixed in 95 per cent alcohol the kidney showed a 

 great retention of iron. This was confined entirely to the cells 

 of the convoluted tubules, and again showed the peculiar locali- 

 zation noted in the previous experiments (K12, K13, K30, K37, 

 K89, and K91) (fig. 2). Some of the tubules were entirely free of 

 iron and in others the cells were heavily laden. This same fact 

 was observed in K102 (six injections) andK105 (five injections), 

 although less iron was present. Those tubules containing the 

 iron were distinctly grouped together. The tubules free of iron 

 also showed the enlarged lumina and cells of decreased size 

 described above. The significance of such a localization is not 

 clear, but two possibilities are suggested. It may be an indica- 

 tion of a selective activity on the part of the different tubules, or 

 on the other hand the localization may be due to some vascular 

 change involving the afferent or even the efferent glomerular 

 arteries, and thereby causing local constriction and an altered 

 and reduced amount of blood to certain tubules. Kobert (41), 

 in his paper on the pharmacology of manganese and iron, records 

 the same type of findings for iron retained in the kidneys, but 

 concludes that the difference in the tubules is due to a difference 

 in the phases of activity in the various cells. Such a conclusion 

 appears invalid in the light of the fact that this selective locali- 

 zation remains over a period of twenty-eight days. 



