160 Prof. B. Moore. The Formation of Nitrites from 



the cell can be transferred to reduce another portion of carbohydrate to fat, 

 or to reduce nitrogenous compounds and build in amino-groups to form 

 proteins. Other examples of such linked reactions are seen in the action of 

 certain bacteria and other unicellular organisms, such as Azotobacter, the 

 nitro-bacteria of the nodules of the Leguminosae, the philothionic organisms 

 which derive stores of energy from the oxidation of sulphur or reduced 

 sulphur compounds, and the iron bacteria which similarly utiHse the energy 

 obtained by oxidation of metallic iron or of ferrous compounds to build up 

 organic carbon compounds from carbon dioxide and water. Such linked 

 reactions require, however, the presence of a living cell containing proto- 

 plasm, possessing as its substratum organic compounds containing both 

 carbon and nitrogen in very complex combinations. Moreover, the substrata 

 of reduced compounds so utilised in linked reactions have demanded at 

 earlier epochs the existence of living organisms for their reduction by the 

 conversion of the energy of sunlight. None of these substances could have 

 existed in a planet cooling down from a red-hot concUtion, on account of their 

 chemical instability at higher temperatures. So also all the bound nitrogen 

 in vegetable and animal organisms, and their decomposition products, such as 

 coal, guano, and nitrates, must at one time have existed as atmospheric 

 nitrogen, for no nitrates or nitro-compounds could have withstood the earher 

 high temperatures. The enormous stores of compounds containing the oxides 

 of nitrogen now used in warfare, agriculture, and industry must have been 

 formed endothermically from atmospheric nitrogen and oxygen with uptake 

 of energy, and whether this occurred through the electric discharge of the 

 thunderstorm or by the agency of living organisms, the first source of the 

 energy, just as in the case of the organic carbon compounds, was the sun's 

 rays. It follows that the agencies by which sunlight was utilised to form 

 reduced compounds of carbon and nitrogen must have existed antecedently 

 to the advent of life, for in its ultimate composition the substratum 

 of proteins necessary to the living organism contains both types of endo- 

 thermically produced radicles. It was such considerations which induced the 

 series of experiments here recorded, which show that the energy of sunlight 

 can be absorbed by dilute solutions of nitrates and institute an endothermic 

 reaction in which the more reactive nitrites are formed even in absence of 

 living organisms, and also that the green cells of plants possess the power of 

 absorbing these nitrites. 



It is well known from the thermo-chemical determinations of Faure, 

 Thomsen, and Berthelot that in the formation of the oxides of nitrogen from 

 their elements the acme of absorption of energy lies at the point of formation 

 of nitric oxide (N2O2), and that the reaction runs endothermically towards 



