ASPECTS OF AN OLD AGRICULTURAL QUESTION. 253 



was locked up ages ago in the coal now brought to our 

 doors, or a century ago in the wood we are now burning, 

 or some months ago in the potatoes or bread we eat to-day, 

 or only a day or hour or two ago in the grass our sheep are 

 feeding on, the fact remains that just the energy locked up 

 in the material in question at the time it was formed is the 

 maximum amount obtainable, and it constitutes the real 

 gain of wealth obtained from the outside universe, con- 

 densed on to our sphere of action by the green plant. 



But another point began to be clear as the establish- 

 ment of the above truth became firmer, namely, that these 

 carbon-compounds are the starting products for the synthesis 

 of the much more complex nitrogenous compounds of which 

 living structure is formed. Somewhere and somehow in the 



o 



living cell, the carbon-compounds referred to are brought 

 into contact with nitrogen, and traces of other elements (of 

 which sulphur and phosphorus are the most important), and 

 worked up into the higher nitrogenous bodies so remark- 

 able for the extraordinary quantities of energy they are 

 capable of liberating, and, what is more important,, of 

 economically utilising. 



Physiologists have shown clearly that in order to obtain 

 the energy necessary to work this apparent miracle of 

 synthesising nitrogenous compounds from carbo-hydrates 

 and nitrogen, the living machinery of the cell oxidises and 

 burns back into carbon-dioxide and water, part of the excess 

 of the stored carbo-hydrates themselves — the cell thus 

 respires, and in this respect behaves as does any living cell 

 of an ordinarv animal. 



Having shown that the functions of the chlorophyll 

 apparatus — to manufacture carbo-hydrates from carbon- 

 dioxide and water, by means of the energy of solar radia- 

 tions, oxygen escaping free — are not only not contradictory 

 of those of the oxygen-respiring living cell — where the 

 burning of part of the gained carbo-hydrates to carbon- 

 dioxide and water occurs as in an animal cell — the path 

 was now clear to inquire into the question of the nitrogen 

 employed in the further syntheses of the more complex 

 substance built up at the expense of the carbo-hydrates. 



