more dangerous than the
other distortion. The indications of this evil, are, the projection of
one shoulder blade more than the other, and, in bad cases, one shoulder
being higher, and the hip on the opposite side more projecting, than the
other. In this case, the spine, when viewed from behind, instead of
running in a straight line, (as in Fig. 7 and 9,) is curved somewhat, as
may be seen in Figures 10 and 11.

This effect is occasioned by the softness of the bones, induced by want
of exercise, together with tight dressing, which tends to weaken the
muscles that are thus thrown out of use. Improper and long continued
positions in drawing, writing, and sleeping, which throw the weight of
the body on one part of the spine, induce the same evil. This distortion
is usually accompanied with some consequent disease of the nervous
system, or some disarrangement of the internal organs.

By comparing Figures 9 and 11, the difference between a natural and
distorted spine will be readily perceived. In Fig. 10, the curved line
shows the course of the spine, occasioned by distortion; the
perpendicular line, in this and Fig. 11, indicates the true direction of
the spine; the horizontal lines show that one shoulder and hip are
forced from their proper level.

[Illustration: Fig. 9.]

[Illustration: Fig. 10.]

[Illustration: Fig. 11.]

BLOOD-VESSELS.

The blood is the fluid into which our food is changed, and which is
employed to minister nourishment to the whole body. For this purpose, it
is carried to every part of the body, by the arteries; and, after it has
given out its nourishment, returns to the heart, through the veins.

The subjoined engraving, (Fig. 12,) which presents a rude outline of the
vascular system, will more clearly illustrate this operation, as we
shall presently show.

[Illustration: Fig. 12.]

Before entering the heart, the blood receives a fresh supply of
nourishment, by a duct which leads from the stomach. The arteries have
their origin from the heart, in a great trunk, called the _aorta_, which
is the parent of all the arteries, as the spinal marrow is the parent of
the nerves which it sends out. When the arteries have branched out into
myriads of minute vessels, the blood which is in them passes into as
minute veins; and these run into each other, like the rills and branches
of a river, until they are all united in two great veins, which run into
the heart. One of these large receivers, called