SECRETION AND EXCRETION 337 



common salt solution by a fish bladder that salt crystallizes out. 

 From the investigations of F. HOFMEISTER and Wo. OSTWALD it may 

 be concluded that the swelling of gelatin-jellies is favored by some 

 salts in accordance with their lyotropic action, while other salts dimin- 

 ish the swelling (see pp. 69 and 70) ; in other words, according to the 

 nature of the dissolved salts, more or less water may be removed from 

 a solution by the swelling of jellies. The extent to which the individ- 

 ual ions in mixtures of electrolytes may be more or less concentrated 

 in the solution which remains after the swelling has received as yet no 

 satisfactory experimental study. But even LUDWIG sought such an 

 interpretation and sought by its aid to explain the proportionately 

 greater excretion of phosphates than of chlorids in the urine. 



LAGERGREEN found a negative adsorption with charcoal and 

 kaolin in solutions of chlorids of Na, K, NH 4 and Mg; in other 

 words, there resulted a concentration of the solution, whereas nitrates 

 show a positive adsorption; in the case of sulphates the adsorption was 

 partly positive and partly negative. F. HOFMEISTER in the case of 

 gelatin found that the absorption of water and of dissolved substance 

 proceeded independently of each other, that the absorption of water 

 from an NaCl solution increased until the concentration reached 13 

 to 14 per cent, and that when the concentration was higher than this, 

 the absorption of water fell again. J. M. VAN BEMMELEN demon- 

 strated that potassium sulphate is split up by manganese dioxid, 

 because K is adsorbed while SO 4 remains in solution (the solution 

 has an acid reaction). Subsequently, similar cleavages were demon- 

 strated by M. MASIUS and L. MICHAELIS. It is thus evident that 

 there exists the possibility of a varying adsorption of salts (and 

 other substances) during swelling; so that an acid fluid (urine re- 

 acts acid) may result from a neutral filtrate. If we now attempt to 

 apply these general facts to the special instances of the concentration 

 of the glomerular filtrate, we shall see that the most important 

 scientific support is lacking. Adsorption experiments with renal 

 substance are especially necessary. The experiments of TORALD 

 SOLLMANN may be explained on the basis of our hypothesis. He 

 found that the percentage of chlorids in the urine was increased by 

 nitrates, iodids and sulphocyanids, and, on the other hand, that it is 

 decreased by acetates, phosphates and sulphates. 



No facts contradict the colloid-chemical conception of urine ex- 

 cretion, but we still lack the special experimental data that should 

 support it. If we recall that none of the other explanations of 

 diuresis are in any better position but that they must cling to vital- 

 istic assumptions, we are compelled to accept the filtration theory as 

 the most advantageous until a better one shall replace it. 



