THE TUBULES 

 Function of the Tubules 



221 



In spite of innumerable experiments made with a view 

 of deciding whether the tubules secrete substances in 

 solution or absorb water, the question cannot be said to 

 have been decided. The chief reasons for this are that 

 in many experiments conditions are so unrehable that 

 no conclusion can be drawn from them, while in other 



2 4- 



RJNGEK. 



Na^So^ 



Tig. 29. — Diuresis and oxj'gen consumption (after Bareroft and Straub). 

 Dotted line = oxygen consumption ; shaded area = amount of urine 

 secreted. 



experiments the results are equally well or equally badly 

 explained on either theory. 



1. Heiclenhain decided the point to his own satisfaction 

 by injecting substances into the circulation and afterwards 

 examining their deposition in the kidney. Using Sodium 

 Sulphindigotate, he showed that shortly after injection 

 the stain appeared in the cells of the tubules, while later 

 on it appeared in the lumen of the tubules. For long 

 these experiments were regarded as proof of tubular 

 secretion, but they are now known to be fallacious. The 



