onward towards the heart. Exercise also induces a more vigorous
respiration, and under increased breathing efforts the lung capacity is
increased and the size of the chest is enlarged. The amount of air
inspired and expired in a given time is much larger than if the body were
at rest. The blood is thus supplied with a much larger amount of oxygen
from the air inhaled, and gives off to the air a corresponding excess of
carbon dioxid and water.

Again, exercise stimulates and strengthens the organs of digestion. The
appetite is improved, as is especially noted after exercise in the open
air. The digestion is more complete, absorption becomes more rapid, the
peristaltic movements of the bowels are promoted, and the circulation
through the liver is more vigorous. More food is taken to supply the force
necessary for the maintenance of the mechanical movements. Ample exercise
also checks the tendency towards a torpid circulation in the larger
digestive organs, as the stomach and the liver, so common with those who
eat heartily, but lead sedentary lives. In short, exercise may be regarded
as a great regulator of nutrition.

Exercise increases the flow of blood through the small vessels of the
skin, and thus increases the radiation of heat from the surface. If the
exercise be vigorous and the weather hot, a profuse sweat ensues, the
rapid evaporation of which cools the body. The skin is thus a most
important regulator of the bodily temperature, and prevents any rise above
the normal which would otherwise result from vigorous exercise. (See secs.
226 and 241).

84. Effect of Exercise upon the Personal Appearance. Judicious and
systematic exercise, if moderately employed, soon gives a more upright and
symmetrical figure, and an easier and more graceful carriage. Rounded