LIFE A DIRECTOR OF FORCE. 



635 



And then, again, how did this substance, once formed, become alive? 

 " Directivity " * appears to have been at work. 



Now the word "directivity" may be widely extended. It not 

 only covers such vegetable products as Sir A. H. Chuech alludes to, 

 but all others which cannot as yet be made in the laboratory; and 

 protoplasm is the most important of all. To make the first atom of 

 protoplasm, directivity from some unknown source must have been 

 present. Was there a pre-existent life without protoplasm, which 

 directed the elements to combine to make it for all future organisms ? 



But as far as we can judge, the first living being must have been a 

 green vegetable of a very simple kind; for no colourless plants, such 

 as microbes or animals, can live on mineral matters. 



The word ** mineral " includes all three conditions — the solid, the 

 liquid, and the gaseous ; but living matter is always solid. We are 

 now concerned only with the directivity in the latter. 



Let us, then, consider the machinery by which life in plants can 

 direct the forces which move matter in their construction. 



The roots absorb water wherein is dissolved necessary mineral 

 salts, forming the ash when the plant is burnt. The stem conveys 

 this water to the leaves. The leaves get rid of much of the water in 

 the form of vapour; they are also recipients of gaseous food (OOj, or 

 carbonic acid gas). They then digest and assimilate the carbon. The 

 first visible organic product, made under the directivity of life, is 

 starch; but in order to avoid its accumulation in the leaves it is con- 

 verted into soluble sugar, and soon conveyed away to places where 

 growth is going on, or else to be stored up again, re-formed as starch 

 in tubers and seeds. 



The "elaborated sap," containing, hke blood, the nourishing 

 matters, then passes back into the trunk and branches and down into 

 the roots; so that every part of the plant can grow. All the above 

 "movements of matter," or "molecular motions," are done under 

 the directivity of life governing the energy displayed. Nothing of the 

 sort exists in the inorganic or mineral kingdom. A crystal is often 

 described as " growing," but its increase in size is only by superficial 

 accretions of the same kind of matter. 



Moreover, life governs many of the chemical changes which take 

 place. Thus various substances, especially carbonic acid and 

 nitrates, are absorbed by the leaves and roots respectively, are decom- 

 posed, and their elements reunited to form " organic " compounds, 

 which have never been founi outside a living being. It was this fact, 

 as stated, which suggested the word " directivity " to Sir A. H. 

 Church. 



* I am indebted to Sir A. H. Church, F.R.S., for this very useful and 

 expressive word, "Directivity." He wrote me : "I coined it many years ago 

 to avoid the use of ' force,' 'energy,' &c., when describing in lectures on organic 

 chemistry the parallelism between the chemist directing in his laboratory physico- 

 chemical forces in the making of a true organic compound and that mysterious 

 something ' which employs the same forces to make the same compound in the 

 plant or animal." 



