The abdominal muscles compress the abdomen and force up the diaphragm which is now relaxed, thus lessening the depth of the thorax.

This pressure forces the air from the lungs and prepares them for another inspiration.
CORRECT METHOD That the lateral-abdominal--more accurately chest-abdominal--breathing is correct and natural for both male, and female, and that the shoulders should remain as fixed as were Demosthenes' under the points of the swords hung over them, is now so generally admitted as to need no argument here.

If any one has still a doubt on the subject let him observe a sleeping infant.

It affords a perfect example of lateral-abdominal breathing, and no one can have a suspicion of sex from any difference in this function.

Among the lower animals sex shows no difference in breathing at any age.