LECTURE X 



METABOLISM AND GROWTH 



IN past lectures I have tried to sketch out for you the 

 development of our knowledge of what may be termed 

 the preliminary stages in plant nutrition up to about 

 the years 1890-1900, viz. the absorption and transport 

 of water and minerals, the acquisition of nitrogen and 

 carbon, and the construction of the first products of 

 photosynthetic activity. I must now add a word or 

 two on the attempts that were made previous to the 

 dawn of the twentieth century on the general metabolic 

 processes taking place in the plant. 



Towards the end of the nineteenth century it had 

 become accepted as a biological axiom that a plant was 

 a living organism in which a most complex series of 

 chemical changes were constantly taking place, described 

 collectively as " metabolic," and that these changes 

 might be arranged in two categories constructive, or 

 anabolic, viz. those connected with the upbuilding of 

 organic matter and the storage of energy, and destructive, 

 or katabolic, those concerned with the disintegration of 

 organic compounds, the release of energy and the excretion 

 of waste. The goal of anabolism was obviously the 

 formation of protoplasm, and the outcome and accompani- 

 ment of katabolism was the manifestation of what we call 

 " life." It was also recognised that the anabolic pheno- 

 mena might be divided into two phases, the first concerned 

 with the acquisition of the raw materials and their 

 construction into those higher compounds to which the 



213 



