Galen scarcely takes any notice of vociferation, except that, in one
place, he states that it exercises the chest and lungs. (De Sanit.
tuendâ, ii, 11.)
Avicenna, in giving an account of vociferation, follows Aëtius. He says,
that it exercises the parts about the mouth and chest; and hence, that
it improves the complexion. He likewise cautions us not to prolong loud
enunciation, lest it occasion a rupture of the vessels. He directs us to
begin moderate, and then strain the voice gradually, and afterwards to
allow it to sink by degrees, (i, 3, 2.)