4: INTBODUCTION. 



manner, though thus far all attempts in this direction have been unavail- 

 ing. All those compounds which have as .yet been made by synthesis 

 are allied to those which result from a long-continued series of chemical 

 changes in the organism, produced by the action of oxygen upon prod- 

 ucts of disintegration. 



6. In their Mode of Growth. — Organized bodies grow by assimila- 

 tion, — the internal deposit of materials by which the unlike become the 

 like. Unorganized bodies grow, or increase in size, by external deposit 

 or accretion. The organized body is dying from the moment of its birth, 

 and requires new materials to repair those losses and for the increase in 

 size. The unorganized body, as the crystal or the stalactite, continues 

 to increase in size so long as fresh particles are deposited upon it. 

 Every part of an inorganic body is therefore alike and independent of 

 the rest, and exhibits the s:\me properties as the whole. The organized 

 body, on the contrary, is made up of a number of dissimilar parts, each 

 of which is more or less dependent upon the others, and each of which 

 requires different materials for its growth and reparation. In the unor- 

 ganized body a small portion serves to determine by analysis the consti- 

 tution of the whole; in other words, it is homogeneous. In the organ- 

 ized body each part is more or less dependent on the remainder, and 

 differs from it in chemical composition ; in other words, it is hetero- 

 geneous. Organic compounds, moreover, from the large quantity of 

 fluid they contain, are usually soft and ductile, while the inorganic body- 

 is hard, rigid, and inflexible, and when once the affinities of its chemical 

 elements are satisfied it remains an inert mass. Within the organized 

 living body all is change. Death and repair ^are ever taking place. From 

 the commencement of its existence its growth, its progress toward 

 maturity, its decline, decay, and death are all made up of an incessant 

 series of changes. It is the constant round of these actions which con- 

 stitutes life ; their study is the subject of physiology. 



It is thus seen that organized are distinguished from unorganized 

 bodies by three cardinal characteristics: 1. The law of nutrition, the 

 most fundamental of all vital laws ; since in virtue of it the organism 

 continues to exist as an active being, and increases from infancy to 

 maturity. 2. The law of development, or differentiation, which causes 

 the organism to pass through the definite cycles of change constituting 

 what we call ages, and leading inevitably to the final changes which we 

 call death. 3. The law of reproduction, another aspect of the first law, 

 in virtue of which the organism gives origin to similar organisms from 

 one generation to another. 



In no example of inorganic matter can any of these characteristics 

 be found. When inorganic bodies are said to grow, their growth is a 

 process of mere aggregation, one part adhering to another similar part. 



