chap. KX\\.\ FILTRATION ANDURINARV SECRETION. 269 



water and salts in solution pass from the blood-vessels 

 into the dilated extremities of the uriniferous tubules, 

 but that albumen does not pass. This would imply a 

 qualitative change in the fluid by filtration, which is 

 contrary to all the results of accurate observation of 

 the physical process. If we accept the filtration 

 process, then, we must admit the passage of albumen 

 through the glomeruli into the tubules. It is to be 

 observed, however, that the conditions in the kidney 

 (only a moderate pressure in the blood-vessels, and the 

 blood being a saline solution) are just the conditions 

 fitted to make the quantity of filtered albumen small. 

 Yet the facts seem to confine us to the conclusion" 

 that the process in the glomerules of the kidney is 

 one by which all the constituents of the blood plasma 

 transude, though in largely different proportions from 

 that in which they exist in the blood. This view is 

 not at present popular among physiologists, though 

 it has been suggested by von Wittich, Kiiss, and 

 others, and that mainly because of the difficulty of 

 accounting for the absence of the albumen in normal 

 urine. It does not belong to this work to discuss 

 that difficulty, though it may be mentioned that the 

 difficulty is, to some extent, met by the view that the 

 active cells of the renal tubules absorb the albumen, 

 and pass it back into the surrounding lymphatics, 

 a view in favour of which, the author believes, much 

 can be said. 



