If a person inspire deeply, he will be able, immediately after, to
hold breath for a time, varying with his health, state of exertion,
or repose. A man, during an active walk, may not be able to cease
breathing for more than half a minute; but, after resting on a chair or
bed, he may refrain from breathing for a minute and a half, or even two
minutes. But if he will prepare himself by breathing deeply, hardly,
and quickly (as he would naturally do after running), and ceasing
that operation with his lungs full of air, then hold his breath as
long as he is able, he will find that the time, during which he can
remain without breathing, will be double, or even more than double the
former. This effect may be rendered exceedingly serviceable, as on
many occasions a man who can hold breath for a minute, or two minutes,
may save the life of another; such as in entering a chamber on fire,
rescuing from drowning, &c.