In front its attachment is to the cartilage at the pit of the stomach.

It also connects with the transverse abdominal muscle.

The diaphragm being convex, in inspiration the contraction of its fibres flattens it downward and presses down the organs in the abdomen, thus increasing the depth of the thorax.

Expiration depends wholly on other muscles.
[Illustration: FIGURE 8.] The muscles so far mentioned are all that need "conscious education;" the others will act with them voluntarily, automatically.

The abdominal muscles relax during inspiration and the diaphragm relaxes during expiration, thus rendering the forces nearly equal, though the strength is in favor of the expiratory muscles.