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Death from drowning is the result of asphyxia, due to the stoppage of a
supply of fresh air to the lungs. There is a certain amount of
stationary air in the lungs, and into this is diffused oxygen from the
fresh air taken in, while the carbonic acid which it has taken from the
blood through the walls of the capillaries is driven out. This process
of exchange is ever proceeding, the whole of it being regulated from the
nervous centre at the base of the brain. When a person gets under water
and cannot swim, there is a natural tendency to struggle, and in the
efforts to respire water is drawn into the windpipe and cough is brought
on. This expels the air from the lungs with the water which threatened
to suffocate him, and as further efforts are made to respire more water
is taken in and has to be swallowed. Meanwhile, the oxygen in the lungs
is gradually diminishing, the quantity of carbonic acid is increasing,
and at length the air in the lungs becomes too impure to effect an
exchange with the blood. Then the blood passing into the heart becomes
venous and the heart begins to send out venous instead of arterial blood
to all parts of the body. Immediately a dull, sickening pain becomes
apparent at the base of the neck, and insensibility rapidly ensues. This
arises from the affection of the respiratory nerve centre. In a short
space of time the face becomes dark and congested through the veins
being gorged with blood, and the heart ultimately ceases to beat.

When a person unable to swim falls into the water, he usually rises to
the surface, throws up his arms and calls for help. This, with the water
swallowed, will make him sink, and if the arms are moved above the head
when under water, he will, as a natural consequence, sink still lower.
The struggle will be prolonged a few seconds, and then probably cease
for a time, allowing him to rise again, though perhaps not sufficiently
high to enable him to get another breath of air. If still conscious, he
will renew his struggle, more feebly perhaps, but with the same result.
As soon as insensibility occurs, the body sinks altogether, owing to the
loss of air and the filling of the stomach with water. There is a
general belief that a drowning person must rise three times before he
finally sinks, but this is a fallacy. The question whether he rises at
all, or how often he does so, entirely depends upon circumstances. A man
may get entangled among weeds, which prevent his com