16 PHYSIOLOGY. 



such as wood, bark, leaves, roots, and flowers ; and in ani- 

 mals, muscles, nerves, tendons, vessels all of which are 

 organs, or instruments for the accomplishment of certain 

 purposes. Inorganic bodies are formed of homogeneous parts, 

 or parts perfectly similar. 



12. Organic bodies are composed of two kinds of elements, 

 chemical, such as oxygen, carbon, and hydrogen, which exist 

 in minerals ; and organic, or proximate, such as albumen, gel- 

 atine, fibrin, &c., such as are never found in inorganic mat- 

 ter. It is because these organic substances are produced by 

 the peculiar forces of organic life, and not by chemical laws, 

 that we cannot decompose and then re-form them, out of 

 the same elements, as we can minerals. For example, we 

 can dissolve alum, salt, or copperas, and then by evapora- 

 tion, crystalize them in the same shape again. 



13. The general properties of organic or inorganic bodies 

 differ in many particulars. In the first place there is a 

 constant warfare going on, between the chemical and phys- 

 ical laws, which govern inorganic matter, and the vital laws 

 which maintain animal life. This conflict commences at 

 the first period of our existence, and is kept up to the moment 

 of our dissolution. Life is enabled, for wise purposes, to 

 wrest portions of matter from the domain of the laws of 

 matter, for a certain indefinite period ; for a while, the 

 vital powers maintain a successful contest, but at last they 

 have to yield, and death gives over the body to the action 

 of the chemical forces. 



14. This power of resisting the mechanical and chemical 

 laws of matter, is shown by the faculty which animal bodies 

 possess of maintaining the same degree of temperature, amid 

 the great changes from heat to cold to which they are exposed ; 

 in the power of changing to chyle and blood, the various 

 forms of food on which they subsist ; and also in their power 

 of forming from these the various tissues and organs of which 

 they are composed, and all in opposition to the general laws 

 of matter. 



