INORGANIC PRINCIPLES. 439 



bonates, the inorganic elements of food do not necessarily undergo any modification in 

 the process of digestion. They are generally introduced already in combination with 

 organic matter, and they accompany it in the changes which it passes through in digestion, 

 assimilation by the blood, deposition in the tissues, and the final transformations that 

 result in the various excrementitious matters ; so that we find the inorganic principles 

 united with the organic matter of the food as it enters the body, and what seem to be 

 the same principles in connection with the organic excrementitious matters. Between 

 these two extremes, however, are the various operations of assimilation and disassimila- 

 tion, from which inorganic matter is never absent. As we have not yet taken up fully 

 the connection of the various inorganic matters with nutrition, it will be convenient here 

 to give a brief review of the different individual principles of this class. 



Inorganic Principles. 



The number of these principles now well established as existing in the human body 

 is about twenty-one. All substances which at any time exist in the body are proximate 

 principles ; but some are found in small quantities, are not always present, and apparent- 

 ly have no very important function. These will be passed over rapidly, as well as 

 those which are so intimately connected with some important function as to render their 

 full consideration in connection with that function indispensable. The following is a 

 list of the most important inorganic principles, excluding those which are excrementi- 

 tious and one or two which are not yet well established : 



Table of Inorganic Principles. 



Proximate Principles. Where found. 



I Oxygen. Lungs and blood. 



Hydrogen. Gases of stomach and colon, and blood. 



Nitrogen. Lungs, intestinal gases, and blood. 



Carburetted hydrogen. Lungs (expired air), intestines. 



Sulphuretted hydrogen. Lungs (expired air), intestines. 



Water. Universal. 



Chloride of sodium. Universal, except the enamel. 



Chloride of potassium. Muscles, liver, milk, chyle, blood, mucus, saliva, bile, gas- 

 tric juice, cephalo-rachidian fluid, and urine. 



Phosphate of lime (basic). Universal. 



Carbonate of lime. Bones, teeth, cartilage, internal ear, blood, sebaceous mat- 

 ter, and sometimes the urine. 



Carbonate of soda. Blood, bone, saliva, lymph, cephalo-rachidian fluid, and 



urine. 



Carbonate of potassa. Blood, bone, lymph, and urine. 



Phosphate of magnesia. Universal. 



Phosphate of soda (neutral). Universal. 



Phosphate of potassa. Universal. 



Sulphate of soda. Universal, except milk, bile, and gastric juice. 



Sulphate of potassa. Same as sulphate of soda. 



Sulphate of lime. Blood and faeces. 



Hydrochlorate of ammonia. Gastric juice, saliva, tears, and urine. 



Carbonate of magnesia. A trace in the blood and sebaceous matter. 



Bicarbonate of soda. Blood (Liebig). 



Gases. The gases (oxygen, hydrogen, nitrogen, carburetted hydrogen, and sulphuretted 

 hydrogen) exist both in a gaseous state and in solution in some of the fluids of the body. 

 Oxygen plays a most important part in the function of respiration ; but the office of the 



