PHYSICAL CHEMISTRY IN MEDICINE. 



amounts of diffusion work would have to be used in order 

 to separate the substances again and to bring about the 

 original differences. This work must also be done by 

 the kidneys, and in two directions, toward the urine and 

 toward the blood. The value of this can also be calcu- 

 lated, a subject which is, however, not within the bounds 

 of this paper. We may call this the selective work of the 

 kidneys. 



The osmotic work of the kidneys is therefore made 

 up of three components the osmotic work of water 

 secretion, that of water absorption, and that of selection. 



Dead material, such as gelatine plates, may also show 

 a power of selection. For a recognition of this important 

 fact we are indebted to HOFMEISTER and his pupil SPIRO. 

 The latter has elucidated these phenomena through 

 physico-chemical principles. 



While, however, a gelatine plate that has absorbed 

 a salt or a dye remains in equilibrium with its surround- 

 ings and is not capable of any further selective activity, 

 the phenomena observed in the kidney are of a dynamic 

 nature. 



The selective function of the kidney is an uninterrupted 

 process, maintained through the active metabolism of its 

 living substance. 



It is not possible to mention here all the other beautiful 

 applications that have been made of physical chemistry 

 to questions in physiology and pathology. Many im- 

 portant advances besides those already noted might be 

 brought up here. Pharmacodynamics may also expect 

 great changes through use of the new theories, as may 

 be concluded from the attempts which are already being 

 made to introduce these new methods into this science. 



