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SCIENCE. 



[N. S. Vol. XXII. No. 569. 



I do not need to enter more fully upon 

 them; what concerns us here is that they 

 secured a wide acceptance for the Heiden- 

 hain theory. But since the pharmacolog- 

 ical study of glandular secretion as com- 

 pared with renal activity has shown that 

 these forms of cellular function are dif- 

 ferent and even opposed to one another in 

 certain respects, and since the behavior of 

 certain pharmacological agents is difficult 

 to harmonize with the Heidenhain view and 

 easier to bring into accord with the theory 

 of Lud^vig, a number of pharmacological 

 studies have been undertaken with a view 

 to testing the validity of the Ludwig the- 

 ory. If, as Heidenhain maintained, the 

 coloration of the kidney is an indication 

 and measure of its normal secretory ac- 

 tivity, it might be expected that by means 

 of experimentally increased diuresis this 

 coloration would show corresponding alter- 

 ations, that is to say, coloration would be 

 intensified in the tubules. With this idea 

 in mind Sobieranski, about ten years ago, 

 began a new study of this subject in my 

 laboratory by means of color injections, 

 carried out according to the Heidenhain 

 method. His results on normal animals 

 led him to the conclusion that dyes were 

 not excreted by the convoluted tubules, as 

 Heidenhain thought from his findings, but 

 in company with the water stream through 

 the glomeruli, wh,ence the dye passed into 

 the tubules and was absorbed into the 

 epithelium, coloring their nuclei. Through 

 the simultaneous reabsorption of water by 

 the tubules, the dye-stuff solution becomes 

 more and more concentrated so that it (the 

 dye) under certain conditions is bound to 

 be separated in a crystalline state in the 

 epithelium. 



This had already been shown to be the 

 case by experiments with sodium sulphin- 

 digotate, but still more clearly by means of 

 experiments with carmine, a dye which is 



better adapted to this kind of experimenta- 

 tion because it does not undergo reduction 

 (with loss of color) in the tissues. Even 

 more surprising and striking were the re- 

 sults obtained on diuresis under the influ- 

 ence of caffeine, sodium nitrate or urea. 

 Here the tubules were found to be very 

 little or not at all colored. It was thus 

 shown that an increase in the secretion of 

 the dye through the tubular epithelium, 

 which the hypothesis of Heidenhain calls 

 for, under these circumstances did not ex- 

 ist. On the other hand, the process be- 

 comes intelligible through the explanation 

 of Sobieranski. These diuretics give rise 

 to diuresis by inhibiting the absorption of 

 water from the urinary tubules, and at the 

 same time prevent the absorption of the 

 coloring matter by the tubular structures. 

 Against this interpretation of Sobieranski 's 

 findings it is possible to offer certain objec- 

 tions, the validity of which we have recog- 

 nized from the beginning. The experi- 

 ments of Sobieranski can be regarded as 

 corroborative evidence of the resorption 

 function of the urinary tubules, but not as 

 positive proof of this function. 



One may approach the subject, also, 

 from an entirely different side. If the 

 process of separating water from the blood 

 in the glomeruli is not an elective secretory 

 process, as in other glands, but is in reality 

 a process analogous to filtration, that is to 

 say, is essentially dependent on physico- 

 chemical conditions, then one would expect, 

 as Tammann has already shown, that to- 

 gether with the free water of the blood 

 (not held by the blood colloids) the dis- 

 solved crystalloid constituents, like urea 

 and salts, would simultaneously filter 

 through; in other words, that with in- 

 creased separation of water these bodies 

 would also be excreted in increased 

 amounts. On the other hand, the colloids 

 and other substances similarly held in the 



