48 INTRODUCTION. 



water, which composes two-thirds of the entire organism, and 

 yet only about four and a half pounds are discharged daily 

 from the skin and lungs, and in the urine and feces. 



The second group enters and is discharged from the body 

 in considerable quantity, and very little remains in the or- 

 ganism ; as common salt, which exists in the urine in a 

 greater proportion than in any of the solids or other fluids. 



The following are the organic substances which are ap- 

 parently indispensable to the constitution of organized tissues : 



Water. 



Basic Phosphate of Lime. 

 Carbonate of Lime. 

 Phosphate of Magnesia. 



" Soda. 



" " Potassa. 



The following are those which appear to have an accessory 

 office in nutrition : 



Chloride of Sodium. 



" " Potassium. 

 Carhonate of Soda. 

 Bicarbonate of Soda. 

 Carbonate of Potassa. 



Sulphate of Soda. 

 " " Potassa. 



The remaining two .principles, sulphate of lime and hy- 

 drochlorate of ammonia, are so obscure in their function that 

 they cannot be definitely put in either of the above groups. 



ORGANIC NON-NITROGENIZED PRINCIPLES. 



(Hydro- Carbons.) 



The principles of this class differ widely from inorganic 

 substances. In the first place, they have a different origin, 



