CHAPTER I. IX 



THE AMOUNT, COMPOSITION, AND CHARACTER OF URINE 



Bi R. G. l'i LE( i. B.A., Ml). 



In the chapters on digestion and metabolism, we have followed I 

 course which food takes with especial reference to the nutrition of 

 body. The excretion of these elements of nutrition is taken up under a 

 number of ihe subdivisions of physiology, viz.. respiration, digestion, 

 kidney function and the skin. In the chapters on digestion attention was 

 called to the fact that the feces, besides containing the indigestible resi- 

 due of the aliment, contain several excretory products which at i 

 time or another have actually been within the body proper. These in- 

 clude normally the pigments of the body and many of the heavier mineral 

 salts, such as iron, magnesium, lime and phosphates; and under abnormal 

 conditions, as when the metals are given as medicine, bismuth and mer- 

 cury. The respiratory system excretes most of the oxygen and carbon. 



Tn this chapter we shall take up the manner in which the body rid- il 



of tin 1 nitrogenous and some of the mineral waste materials. Even at 

 the risk of repetition, it will he advantageous 1" recapitulate certain fi 

 concerning the essential chemical structure of the urinary constituents, 

 so thai we may lie in a position to appreciate the kidney function in 

 health and disea 



We now know that the kidney docs not form any of the specith n- 



stitucnts of it- secretion (excepl hippuric acid". These substances are 



formed in the various tissues of the body, and are brought to the kidneys 



by the blood, where they are eliminated Bui while the constituents are 

 unchanged in chemical composition in the urine from that in which they 

 are found in ihe blood, they do occur in greatly changed proporti< 

 It is this variation in the concentration of the urinary constituents in 



the Mood and the urine which presents the most important and at the 



same time the mosl difficull question in the physiology of the kidney. 

 In the following table ihe percentag imposition of the blood plasma is 



compared with ihat of an average sample of human urine i 

 column gives ihe change in concentration which eacl lituenl un 



•joes in passiii'_ r through the renal fill' 



