into action a part
of the muscular system? Give the experiment that illustrates this
principle. 201. Why should a child he taught to stand erect? 202. How
can round shoulders acquired by habit be remedied?

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[Illustration: Fig. 50. A proper position in sitting.]

203. _The child should be taught to sit erect when employed in study
or work._ This attitude favors a healthy action of the various organs
of the system, and conduces to beauty and symmetry of form. Scholars
are more or less inclined to lean forward and place the elbow on the
table or desk, for support and this is often done when their seats
are provided with backs. Where there is a predisposition to curvature
of the spine, no position is more unfavorable or more productive of
deformities than this; for it is usually continued in one direction,
and the apparent deformity it induces is a projection of the
shoulders. If the girl is so feeble that she cannot sit erect, as
represented by fig. 50, let her stand or recline on a couch; either is
preferable to the position represented by fig. 51. In furnishing
school-rooms, care should be taken that the desks are not so low as to
compel the pupils to lean forward in examining their books.

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203. Why should the erect attitude be assumed in sitting?

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[Illustration: Fig. 51. An improper position in sitting.]

204. _The muscles, when exhausted, cannot endure continued effort._
When the energies of the muscular system have been expended by severe
and long-continued exercise, or the brain and nervous system
prostrated by protracted mental effort, the muscles are unfitted to
maintain the body erect in standing or sitting for a long time, as the
nervous system, in its exhausted state, cannot supply a sufficient
amount of its peculiar influence to maintain the supporting muscles of
the body and head in a state of contraction. Hence, a child or adult,
when much fatigued, should not be compelled to stand or sit erect in
one posture, but should be permitted to vary the position frequently,
as this rests and recruits both the muscular and the nervous system.

205. _A slight relaxation of the muscles tends to prevent their
exhaustion._ In walking, dancing, and most of the mechanical
employments, there will be less fatigue, and the movements will be
more graceful, when the muscles are slightly relaxed. When riding in
cars or coaches, the sys