322 THE URINARY APPARATUS 



The odor is due to the presence of aromatic com- 

 pounds. 



Composition of Urine: 



Water 1500.00 c.c. 



Total solids 72.00 gm. 



Urea 33.18gm. 



Uric acid (urates) 0.55 gm. 



Hippuric acid (hippurates) 0.45 gm 



Kreatinin, xanthin, hypoxanthin, guanin, 



ammonium salts, pigments, etc. . . 11.21 gm. 



Inorganic salts, sodium and potassium sul- ^ 

 phates, phosphates, and chlorides; mag- 

 nesium and calcium phosphates. . . I 27.00 gm. 



Organic salts: lactates, acetates, formates I 

 in small amounts 



Sugar a trace. 



Gases nitrogen and carbonic acid. 



Urea, being the most abundant and important 

 organic compound of the urine, will be described. 

 It is present to the amount of 2 to 3 per cent. It is 

 found after analysis of the urine to consist of a 

 colorless, neutral substance, crystallizing in long, 

 silky needles. It is composed of carbon, oxygen, 

 nitrogen, and hydrogen (CON 2 H 4 ) . The daily quantity 

 excreted amounts to 30 to- 34 grams. It is the end- 

 product of the protein metabolism which has gone on 

 within the body, and the quantity excreted in the 

 urine is dependent upon the amount of protein food 

 consumed and upon the degree to which the protein 

 constituents of the tissues have undergone metabolic 

 changes. 



THE SKIN 



The skin is the structure investing the entire outer 

 surface of the body, blending with the mucous mem- 

 branes which bound the cavities leading into the 

 body, as the mouth, etc. Its dimensions vary in 

 thickness in different parts of the body, from ^ to 



