The muscles which act when we sneeze or hiccough are of this kind.

The arm and the hand do not act unless we wish them to do so.

Suppose it were the same with the heart.
We should have to stay awake all the while to keep it going, because it would not act when we were asleep.

The same is true of our breathing.

We breathe when we are asleep as well as when we are awake, because the breathing muscles work even when we do not think about them.
~10.~ The stomach, the intestines, the blood-vessels, and many other organs within the body have this kind of muscles.