84 ON THE PLANT-CELL. 



I call those assimilated matters which have been mentioned above in 

 the chapter on the substances contained in plants. We can only place 

 in this class those substances which are produced and exist in the 

 simplest cells, and which are necessary universally for the growth of 

 the plant- cell. I do not say that those mentioned above are all, as 

 subsequent researches may add to their number by the discovery of 

 unsuspected relations. There is, for instance, resin, which, though fre- 

 quently present, is excluded because we cannot detect its transitions to 

 the assimilated matters as we can in the fixed oils. In this way we may 

 draw a permanent and useful distinction between assimilated substances 

 and secretions. I would, however, disclaim here any analogy that may 

 be supposed to exist between these substances and those of the animal 

 kingdom, and must insist on regarding these terms as connected with 

 ideas belonging to the vegetable kingdom alone. 



There can be little doubt that all the foregoing processes of decom- 

 position and recomposition of the substances of which the plant-cell is 

 composed have their foundation in well-known chemical powers and laws. 

 That the elements of which the plant-cell is composed obey the same 

 laws in the cell as out of it, seems warranted by the strongest presump- 

 tions of inductive inquiry. All the elements of which plants are com- 

 posed are derived from the inorganic world, and the combinations which 

 carbon, hydrogen, oxygen, nitrogen, &c. enter into in the plant take 

 place under the influence of the properties or powers which they possess 

 independent of the plant-cell. It is for those who suppose that these 

 substances undergo some change in passing into the organism to bring 

 forward some proof of such a change. So long us this proof is wanting 

 (and it ever will be), we must regard it as true that all the chemical laws 

 find uncontrolled exercise in the organism. The activity of the modern 

 school of chemists, Liebig and his followers, Dumas, Mulder, &c., lead 

 us from another point of view to the same result*. Their labours have 

 placed the perfect identity of the elements and processes which go on in 

 and out of the body upon the most satisfactory inductive basis. Liebig 

 and Mulder especially have shown that, if we analyse the course of 

 changes which occur in the elements composing an organism according 

 to the laws of inorganic chemistry, we come to the same results as 

 though they were independent of the organic body. 



The questions to be solved in this department of vegetable physiology 

 are, first, what are the compounds, and what the chemical processes, by 

 which the simplest plant-cells are formed ; and, secondly, what are the 

 compounds, and in what way are formed the substances, which are con- 

 tained in every plant-cell. For a knowledge of the compounds, am- 

 monia, carbonic acid gas, and water, which are every where and 

 universally required for the formation of the assimilated matters, we 

 are indebted to the chemists, De Saussure, Liebig, and others. Liebig * 

 has rightly exposed the absurdity of those who attempt to explain all 

 organic phenomena by what takes place in the elements, away from an 

 organism. There is, however, one fact which occurs in inorganic bodies 

 which exercises the most important influence in organic combinations. 

 It is, that bodies will enter much more freely into union with each other 

 at the moment they are released from other combinations than at any 

 other time. A body in this condition is said to be in statu nascenti, in 

 a nascent state. Of the substances which constitute the food of plants, 



* Chemistry in its relation to Physiology and Pathology. 



