ON VITAL PRODUCTION 85 



CO2 in the atmosphere and dissolved in fresh and sea water 

 than the plants are able to utilise — that is to say, there is a 

 surplus of both water and carbonic acid on the earth. 



But this is not the case with nitrates and other inorganic 

 nitrogen compounds, which are quite indispensable for the 

 nutrition of plant life. There is an enormous quantity of ele- 

 mentary nitrogen in the atmosphere, but this is unavailable, for, 

 in order to utilise it, plants must have it in combination with 

 oxygen (as nitrous and nitric acids), or with hydrogen (as 

 ammonia). Some nitrogen is always being combined with 

 oxygen as the result of electric discharges in the atmosphere, 

 and even under the influence of solar radiation ; but, on the other 

 hand, some nitrate, nitrite, and ammonia are always being 

 decomposed into elementary nitrogen by certain bacteria present 

 in water and soil. Therefore the total amount of nitrogen in the 

 forms of nitrate, nitrite, and ammonia, and thus available for 

 the nutrition of plants, is nearly constant, and certainly does not 

 change appreciably during very long periods of time. That 

 means that the total average quantity of vegetable life on the 

 earth is practically the same from year to year. 



And that being so, the total average quantity of animal life 

 on the earth is also practically the same from year to year over 

 a great lapse of time, for all animal life depends for its continu- 

 ance on vegetable life. There is a certain balance between the 

 two kingdoms of life. In restricted areas of land and sea, and 

 for restricted periods of time, either the plants or animals may 

 predominate ; but in the long-run there is a relation between the 

 two masses of animal and plant substance, and this relation is 

 a nearly constant one. If animal life becomes temporarily very 

 abundant, vegetable life must decrease, because it is being used 

 up to a greater extent than is normal, and this condition will in 

 turn lead to a diminution of animal life. 



Production and Consumption. — The reader will now see what 

 is meant by " vital production." All animals eat organised 

 substance — fats, proteids, and carbohydrates contained in the 

 tissues of other animals and plants. They reduce these sub- 

 stances to the forms of water, carbonic acid, and certain nitro- 

 genous residues, utilising the contained available energy for the 

 production of mechanical work and heat. Then the working sub- 

 stance is thrown out of circulation and is no longer available for 

 the sustenance of the animal organism. The latter is a consumer. 



All the time solar energy is, so to speak, running to waste. 



