Life — Vital Or</ans. 65 



as called organic chemistry know that the substances consti- 

 tutins^ the structure, and contained in the liquids and solids 

 of plants and animals, are in large proportion composed of 

 peculiar combinations of the simple elements, formed only in 

 foodies which possess or have had life, and which cannot be 

 prepared artificially by the chemist from purely mineial con- 

 stituents. Of these may be mentioned cellulose, the substance 

 composing the main bulk of the solid parts of vegetables ; alhumen, 

 fibrine, and others, whicli occur in modified forms both in vege- 

 table and animal bodies ; gelatine, an important constituent of 

 the bones, skin, &c., of animals; together with various matters 

 solid or liquid which occur in tlie interiorof the substance of animals 

 and vegetables, such as starch, oils, fat, gums, &c. A knowledge 

 of chemistry teaches us that these matters belong exclusively to 

 bodies which have possessed life. Thus we see that living things 

 have what we may call compound chemical elements, known to 

 chemists as proximate principles. But how these present them- 

 selves in the first instance, and what their relation is to the 

 phenomena of life, chemistry by itself can but partially ex- 

 plain. 



The terms organic and inorganic are now tolerably familiar to 

 every one as used in reference to the various kinds of bodies 

 forming the earth and its inhabitants. The word organ signifies 

 an instrument or apparatus, and in natural science it is used in 

 the especial sense of an instrument by which some vital function 

 is performed. Thus in man and the higher animals we have 

 <Mgans of sense ; as the eye, the instrument by which we receive 

 most of our sensations of form, but more particularly of colour ; 

 the ear, the instrument which conveys to the mind the sensations of 

 sound, &c. in man and the higher animals life is so complicated 

 a phenomenon that the organs are very numerous and diverse, 

 and tliey admit of classification under many different heads ; the 

 firinctions are for the most part distributed to different and sepa- 

 Tate organs ; this being in general a mark of perfection in the 

 ■scale of organization. Down to a very low point in the animal 

 kingdom, we find systems or classes of organs, of different kinds, 

 associated in the same body : organs of digestion, respiration, 

 &c., of motion, and of sense, localised in particular parts of the 

 frame, and, although acting in concert, incapable of taking on 

 the functions of each other. 



When we pass over from the animal to the vegetable kingdom, 

 we leave behind the organs of sense and motion ; tliose connected' 

 ■with nutriticm and reproduction alone remain— that is to say, 

 speaking in a general sense, and without reference to certain 

 minute and imperfectly studied forms, which are revealed to us by 



VOL. XVII. Y 



