28 HUMAN PHYSIOLOGY. 



N are distinguished for the narrow range of their affinities, and for 

 their chemic inertia. C possesses the great atomic cohesion. O is 

 noted for the number and intensity of its combinations. 



As the properties of the compounds formed by the union of ele- 

 ments must be the resultants of the properties of the elements them- 

 selves, it follows that the ternary compounds, starches, sugars, and 

 fats must possess more or less inertia, and at the same time insta- 

 bility ; while in the more complex proteids, in which sulphur and 

 phosphorus are frequently combined with the four principal elements, 

 molecular instability attains its maximum. As all the foregoing com- 

 pounds possess in varying degrees the properties of inertia and 

 instability, it follows that living matter must possess corresponding 

 properties, and the capability of undergoing unceasingly a series of 

 chemic changes, both of composition and decomposition, in response 

 to the chemic and physical influences by which it is surrounded, 

 and which underlie all the phenomena of life. 



PRINCIPLES OF DISSIMILATION. 



In addition to the previously mentioned compounds, viz., carbo- 

 hydrates, fats, proteids, and inorganic salts, there is obtained by 

 chemic analysis from the tissues and fluids of the body : 

 i. A number of organic acids, such as acetic, lactic, oxalic, butyric, 



propionic, etc., in combination with alkaline and earthy bases. 

 2.. Organic compounds, such as alcohol, glycerin, cholesterin. 



3. Pigments, such as those found in bile and urine. 



4. Crystallizable nitrogenized bodies, such as urea, uric acid, xanthin, 

 hippuric acid, creatin, creatinin, etc. 



While some few of these compounds may possibly be regarded as 

 necessary to the physiologic integrity of the tissues and fluids, the 

 majority of them are to 4>e regarded as products of dissimilation of 

 the "tissues and foods in consequence of functional activity, and 

 represent stages in their reduction to simpler forms previous to being 

 eliminated from the body. 



