244 



NUTRITION 



Urine is a yellowish clear liquid of a specific gravity of from 1017 to 

 1020, acid in reaction, with a bitter saline taste and a characteristic 

 odor. For short times during the day, especially after meals, the 

 reaction may be ,slightly alkaline, but the normal mixed urine of the 

 twenty-four hours appears to be always somewhat acid due to the acid 

 phosphates of sodium, calcium, and potassium. The specific gravity is 

 normally in general inverse proportion to the quantity; to find approxi- 

 mately the- number of grams of dissolved solids, multiply the last two 



FIG. 130 



The circulation about the convoluted tubules. Observe the contrast between the straight 

 and large arterioles and the tortuous veinlets. (Bates.) 



figures of the specific-gravity number by 2.3 (Trapp). In fever, because 

 usually little liquid and food are taken and because in consequence the 

 tissues katabolize themselves, the urine is scanty, highly colored, and of 

 high specific-gravity. The yellowness of urine is due to urochrome and 

 to a slight extent to urobilin, especially in disease, while other pigments- 

 are present in small amounts under certain conditions:- uroerythrin, 

 hematoporphyrin, and certain chromogens. The odor of urine is due 

 to the contained aroma tics (phenol-ska toxyl, kresol, etc.), combined with 



