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SCIENCE. 



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



however, that it is not combined with the 

 blood tissue. It has long been known that 

 dissolved hemoglobin and injected albumin 

 passed through the kidney into the urine. 

 It is also shown by direct microscopical 

 investigation that these bodies pass through 

 the glomeruli. And, as in the case of urea 

 and salts, this excretion of proteids through 

 the glomeruli has been shown by experi- 

 ments by Dr. Schmidt and Dr. Loewi in 

 my laboratory to be a mechanical filtration. 



This specific excretion of uric acid, etc., 

 can not be increased by any of the known 

 diuretics. The action of diuretics, there- 

 fore, can surely not be explained by the 

 supposition that there is a stimulation of 

 the secretory activity of the kidneys. And, 

 moreover, a specific renal secretion is some- 

 thing quite different from the secretory 

 activity of the glands, for the typical gland- 

 ular poisons, like pilocarpine, not merely 

 are without influence on diuresis in general, 

 but have no effect whatever on the excre- 

 tion of uric acid, phosphoric acid, etc. If, 

 then, the filtration of the watery constitu- 

 ents of the blood is highly probable, it fol- 

 lows that as a means of saving water there 

 must be a compensatory resorption in the 

 tubules analogous to the process of resorp- 

 tion from the alimentary canal. In the 

 case of' the intestinal tract large quantities 

 of fluid are secreted from the mouth, 

 stomach and small intestines, even to the 

 amount of several liters in twenty-four 

 hours, which is later reabsorbed in the 

 large intestine, especially in the colon, re- 

 sulting in the semisolid feeces. And a sim- 

 ilar process may be conceived to go on in 

 the kidneys. 



We have undertaken to determine wheth- 

 er this conception is correct. If under 

 normal conditions such a process of con- 

 centration occurs in the tubules, one would 

 expect a diarrhoea (that is, a flow of un- 

 concentrated fluid from the blood) to re- 



sult from elimination of or injury to these 

 parts, just as there results a flow of watery 

 faeces if the colon be removed or its cells 

 paralyzed by poisons, or if the contents of 

 the intestines are rendered incapable of 

 absorption by the addition of certain salts. 

 With this thought in mind Ribbert long 

 ago conducted experiments involving the 

 removal of the medulla of the kidney, as a 

 result of which he did, in fact, observe an 

 increased secretion of a very dilute urine 

 in rabbits. Similar experiments were un- 

 dertaken by Dr. Hausmann and myself 

 three years ago, by means of a somewhat 

 modified operative technique and especially 

 with the aid of quantitative analysis of the 

 urine. In rabbits from which the right 

 kidney had been removed previous to op- 

 eration on the left kidney, we found the 

 excretion of urine increased three or four 

 times, just as did Ribbert, and observed a 

 change from a concentrated mucus-like 

 urine before the operation to a light-colored 

 watery urine of low specific gravity after 

 the operation. Quantitative analysis fur- 

 ther gave the noteworthy result that what- 

 ever might be the normal content of chlor- 

 ides and urea, after the operation the con- 

 tent always approximated that of the blood 

 serum; for example, if the normal content 

 of sodium chloride in a diet poor in this 

 salt averaged 0.1 per cent, or in a diet rich 

 in sodium chloride approximated 2-3 per 

 cent., after the operation there would re- 

 sult in each case a percentage of sodium 

 chloride which varied within the narrow 

 limits of 0.6 to 0.8 per cent. This result 

 seemed to speak strongly for the resorption 

 theory. The resorption activity of the kid- 

 ney may be influenced by pharmacological 

 means as well as by removal of the urinif- 

 erous tubules. One would expect, as in the 

 case of the intestines, that salts would check 

 resorption from the tubules, and, further, 

 that as in the case of the intestines, the 



