CHAPTER VIII 

 THE APPLIED PHYSIOLOGY OF EXCEETION 



MUCH discussion has taken place as to the difference 

 between a secretion and an excretion, and as to whether 

 certain organs are to be regarded as secretory or excre- 

 tory in function. The simplest way of looking at the 

 matter, for clinical purposes at least, is to define as an 

 excretion any waste matter which is discharged from the 

 body and is incapable of being further utilized, and to 

 regard any organ which is responsible for getting rid of 

 such matters as excretory in function, whether it merely 

 picks them out of the blood or builds them up from 

 simpler compounds before getting rid of them. From 

 this point of view the excretory organs of the body, and 

 the waste substances which they discharge, may be 

 arranged as follows : 



Organ. Excretion, 



Kidney ... ... Waste products of nitrogenous metabolism, 



soluble mineral matters, and water. 



Liver Waste products of the red blood corpuscles. 



Lung Waste products of 'carbonaceous' meta- 

 bolism and water. 



Intestine ... ... Unabsorbed residues of food and of the 



digestive juices, and some less soluble 

 mineral matters e.g., calcium and iron. 

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