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Full text of "Man In The Modern World"

CLIMATE AND HUMAN HISTORY
generally below par. Their fertility is very low; there is much infant
mortality among the calves; growth is slow and stunted; milk yield
is subnormal.
Much search has been made for the causes of this state of affairs.
Bacteria have been blamed, and other parasites, and poisonous plants,
But all these were gradually eliminated. It became more and more
evident that the cause was some deficiency in the beasts' food; and
since the food they eat draws all its supplies (save carbon and oxygen
from the inexhaustible air) from the soil, the deficiency must ultim-
ately lie in the soil.
Chemical analysis has confirmed this verdict. The cause of this
poor performance and actual loss, specially grave in dry countries
like Africa and Australia, is a deficiency of one or more of the elements
supplied to plants from the mineral salts of the soil. The commonest
deficiency is that of phosphorus or of calcium—or of both at once,
Since both are necessary ingredients of bone, a shortage of cither will
prevent proper bone growth. Both arc also necessary for the uni*
versal processes of metabolism in the body; and if the supply falls
short of the vital minimum needed for tissue life, the tissues draw on
the reserves held in the skeleton. The mineral framework of the bones
is redissolved to be used up by the living cells, hungry for the missing
elements, and the skeleton grows weak and soft. The milk too grows
poor in calcium and phosphorus, the calf has to go short of them, and,
as he is a rapidly growing organism, feels the lack even more acutely
than his parents.
The depraved appetite for carcasses and bones is a last resort for
getting back some of the missing elements into the system. It is,
however, often disastrous, for many animals thus eat disease-produc-
ing bacteria in the decaying bones, and develop serious illness from
this cause; and even if they avoid poisoning, the mineral shortage
eventually becomes so acute that the animal sickens and dies. In
other cases, mere stunting is the chief result. In the Falkland Islands,
for example, whose pastures are very short of calcium, an ox will
hardly reach five hundred pounds in weight, and the offspring of
good breeds of horses grow up no bigger than ponies,
The symptoms vary a good deal from place to place, largely accord-
ing as the defect is a defect mainly of phosphorus,—perhaps the com-
monest condition,—-or of calcium, or of both, But they all agree in
taking origin in a lack of necessary bone-building elements.
Here and there, though much more rarely, the cattle former
attempts to ply his trade on areas where there is a shortage of other
constituents, When the missing clement is iron, as in parts
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