56 E. J. STIEGLITZ 



Besides prolonging the period of elimination of iron, the accu- 

 mulative retention block decreases the quantity excreted. K72 

 was the first experiment which convincingly demonstrated this. 

 Normally, the first sample of urine after an injection shows a 

 very deep blue reaction with hydrochloric acid and ferrocyanide, 

 a reaction read as + + + , followed by one of + + intensity, and 

 then one of + about five hours after the injection. After the 

 last administration (the fifth) in K72 only one sample showed 

 iron and that was a single plus, 1.5 hours after the injection. 

 Apparently very little iron was excreted, despite the fact that 

 the usual dose was given intravenously. This decrease in the 

 amount secreted was also noted in experiments K89, K91, K102, 

 and somewhat in K105. No exact quantitative studies were 

 made, but the colorimetric estimation is amply delicate to indi- 

 cate the marked decrease. Together with the increased duration 

 of the elimination, this fact is significant in yielding further sup- 

 port to the conception of secretion in contradistinction to reab- 

 sorption by the convoluted tubules. 



Use was made in some of these investigations on the nature of 

 iron retention of the phenolsulphonephthalein functional test of 

 Rowntree and Geraghty (55, 56), which has been shown to be 

 secreted by the convoluted tubules (55, 30, 57) and is extensively 

 used clinically with considerable confidence and success and has 

 proved far superior to other test substances, such as methylene 

 blue (58), indigocarmine (3), rosaniline (59, 60, 61), potassium 

 iodide (62, 63), and hemoglobin. At best, however, the intro- 

 duction of such foreign substances for an estimation of functional 

 renal efficiency is inconclusive, and a study of secretion of the 

 normal constituents of the urine by the newer methods of bio- 

 chemistry is perhaps a better indicator of the functional condi- 

 tion in disease. (Austin, (57)). In the rabbit a dose of 0.5 cc. 

 or 0.03 gram of phenolsulphonephthalein given intravenously 

 was used. The average normal excretion in eight tests was 61 

 per cent lor the first, 8 per cent for the second, or 69 per cent for 

 the two hours. In K72 the first normal reading was 33 per cent, 

 7.5 per cent, or 40.5 per cent for the total of two hours, while a 

 test made after three injections of iron read 17 per cent, 4 per 



