Water in Relation to Health and Disease. 
743 
Suspended particles carried into the streams by effluent water 
used in washing the ores. It is only in exceptional cases that 
any of these substances are found to exist in dangerous pro- 
portions in a dissolved state. In times of flood the suspended 
matter, as we have already pointed out, is left on the grass as 
what is termed “ scum.” Injury arising from herbage contami- 
nated with it is believed to have been much greater than that 
which has arisen from drinking polluted water, but in a large 
number of cases the poison has been derived both from the 
herbage and the water direct. 
The Rivers Pollution Commission established the fact that, of 
all forms of industry, lead mining is the one which has most 
seriously affected animal health. In Cornwall and Wales, 
where it is most extensively carried on, not only were fish 
poisoned in the polluted streams, but many cases of disease 
and death in cattle and horses, as well as in poultry, were 
adduced by farmers whose stock were pastured on the river 
banks. Lead mines yield lead mostly as galena (sulphide of 
lead), mingled with large quantities of various kinds of rock. 
The operation of extracting the ore consists of crushing and 
washing it, when the rocky matters with more or less finely 
powdered ore are carried away into the rivers, leaving behind 
the greater part of the heavier sulphide. In the form of galena 
lead is not so destructive as when it exists as carbonate of lead. 
Small quantities of the latter are sometimes met with in mines, 
and as it cannot be profitably separated, it is allowed to escape 
with the washings, and is no doubt responsible for much of the 
injury resulting to stock from lead pollution of mining rivers. 
Disease resulting from the ingestion of this poison usually 
assumes a chronic form, and the symptoms it induces are very 
characteristic. Loss of condition and an unthrifty appearance 
are the first indications of ill health ; then follow stiffness of the 
limbs, with a desire to lie down, and a dull, lowering expression. 
The bowels are constipated and the fasces black. Soon the joints 
or the sinews, or both, become swollen and painful, and lame- 
ness in one, two, or all the limbs appears, and the body becomes 
tucked up and the back arched and rigid. Paralysis more or less 
complete, colic, and — in acute cases — frenzy are sometimes pre- 
sent. In protracted cases the bones of the head and extremities 
are enlaiged and soft. Pregnant animals abort, and cows and 
mares repeatedly miss service as the result of lead sickness. 
Although disease from the other substances named is much 
less common than that arising from lead, all it need hardly 
be said are capable of impairing health and of causing fatal 
sickness. The danger arising in these as in other instances of 
