MECHANISM OF RENAL SECRETION 73 



Two conspicuous differences between these results and those 

 found for ferric iron stand out. The first of these is the much 

 longer period of elimination (about 100 minutes, or one-third, 

 longer), and the second the fact that the secretion of water is 

 less inhibited, while the initial diuresis is quite marked. In 

 connection with the prolongation of the period of elimination 

 we can offer as explanation the fact that the ferrocyanide, being 

 diffusely distributed through the tissue spaces all over the body, 

 and probably retained there for some time, is more gradually 

 delivered to the kidneys. The obvious tendency for the ferro- 

 cyanide salt to be scattered in the body, in contradistinction to 

 the localization of the ferric ion, makes such an explanation con- 

 ceivable, particularly as we have no clue to the exact and specific 

 route of the ferrocyanide from the blood to the urine. From the 

 histologic preparations (K29, K49) its entrance into the urinary 

 passages appears quite incidental to its general diffusion, while 

 the ferric iron is specifically focused and secreted. 



Sollmann (81), in a discussion of diuresis, states that sodium 

 ferrocyanide lowers the per cent of chlorides in the urine, but 

 the absolute amount is increased, and concludes that the essential 

 factor in the mechanism of chloride retention is the lowered 

 quantity of the unbound sodium chloride in the serum. Sodium 

 chloride is freed from its combination by NO3, I, and SCN, all 

 of which raise the chloride concentration, but acetate, ferro- 

 cyanide, phosphate and sulphate ions, urea and glucose do not 

 free the NaCl and therefore repress its excretion. In another 

 paper (82) on comparative diuresis of different salines he states: 

 *'the diuretic effect is proportional to the dissociation and a 

 specific diuretic action." That 'specific diuretic action' is, in all 

 probability, the alteration of the hydration capacity of the body 

 colloids. 



Fischer (18, p. 51) includes in his series of anions inhibiting 

 the hydration of colloids phosphate, sulphate, acetate, and sul- 

 phocyanate, all of which are also reported by Sollmann (81) as 

 freeing sodium chloride from its combinations. Likewise, 

 among the non-electrolytes, glucose decreases the hydration 

 capacity, but urea increases it. Therefore, with the exception 



