school. The desks should not be too low, causing a forward stoop; or too
high, throwing one shoulder up and giving a twist to the spine. If the
seats are too low there will result an undue strain on the shoulder and
the backbone; if too high, the feet have no proper support, the thighs may
be bent by the weight of the feet and legs, and there is a prolonged
strain on the hips and back. Curvature of the spine and round shoulders
often result from long-continued positions at school in seats and at desks
which are not adapted to the physical build of the occupant.

[Illustration: Fig. 29.--Section of the Knee Joint. (Showing its internal
structure)

A, tendon of the semi-membranosus muscle cut across;
B, F, tendon of same muscle;
C, internal condyle of femur;
D, posterior crucial ligament;
E, internal interarticular fibro cartilage;
G, bursa under knee-cap;
H, ligament of knee-cap;
K, fatty mass under knee-cap;
L, anterior crucial ligament cut across;
P, patella, or knee-cap
]

A few simple rules should guide teachers and school officials in providing
proper furniture for pupils. Seats should be regulated according to the
size and age of the pupils, and frequent changes of seats should be made.
At least three sizes of desks should be used in every schoolroom, and more
in ungraded schools. The feet of each pupil should rest firmly on the
floor, and the edge of the desk should be about one inch higher than the