SOILS AND AGRICULTURE OF NORFOLK. 
351 
( B ) Organic. — The starches and sugars so formed are 
then passed into the circulation of the plant, and are, with 
nitrogen and other elements, built up into its body tissue 
especially as proteins, that is the converse nitrogenous 
bodies forming the bulk of the dry matter of the plant. 
It is to this power of producing organic bodies by the 
synthesis of its elements that the economic value of plants 
is due, for animals, whose tissues are also composed mainly 
of proteins, can only take up the necessary nitrogen by 
assimilating already manufactured nitrogenous bodies, and 
so are entirely dependent on plants for their food, as, in 
addition to the formation of proteins, the body heat of an 
animal is maintained by the energy liberated in its tissues 
from the combustion of sugars, also derived from the plant. 
Animals are true parasites on plants, and obtain food directly 
from consumption of plants. It is obvious that as the plant 
takes in solution from the soil, all the inorganic food it 
requires, when the crop is gathered and removed all 
these constituents are permanently lost to the land. It 
is also obvious that unless every year more of these essential 
elements are rendered available to replace what is taken out, 
sooner or later the crop will be starved for lack of food. 
Again, unless there is sufficient water to dissolve the 
soluble salts the plant will be unable to take them up, and 
may be starved from inability to absorb enough inorganic 
food. The most important source of nitrogen in soils is from 
the dead bodies and excreta of animals and also from the 
decaying tissue of the previous season’s crop, and in 
agricultural practise this supply is carefully regulated. 
Animals are kept and fattened in yards, and their excreta, 
mixed with straw, is stored and then applied to the land. 
The fattening is a costly process, as rich and expensive 
foodstuffs have to be bought and given to the animals in the 
later stages of their cramming, and the farmer often finds he 
has made a heavy loss on each animal sent to market. 
