and foot often "get
asleep" by deep pressure on the nerves of the thigh.

Experiment 137. Press the ulnar nerve at the elbow, the prickling
sensation is referred to the skin on the ulnar side of the hand.

Experiment 138. Dip the elbow in ice-cold water; at first one feels
the sensation of cold, owing to the effect on the cutaneous
nerve-endings. Afterwards, when the trunk of the ulnar nerve is
affected, pain is felt in the skin of the ulnar side of the hand, where
the nerve terminates.

Chapter XI.

The Special Senses.

308. The Special Senses. In man certain special organs are set apart
the particular duty of which is to give information of the nature of the
relations which he sustains to the great world of things, and of which he
is but a mere speck. The special senses are the avenues by which we obtain
this information as to our bodily condition, the world around us, and the
manner in which it affects us.

Animals high in the scale are affected in so many different ways, and by
so many agencies, that a subdivision of labor becomes necessary that the
sense avenues may be rigidly guarded. One person alone may be a sufficient
watch on the deck of a sloop, but an ocean steamer needs a score or more
on guard, each with his special duty and at his own post. Or the senses
are like a series of disciplined picket-guards, along the outposts of the
mind, to take note of events, and to report to headquarters any
information which may be within the range of their duty.

Thus it is that we are provided with a number of special senses, by
means of which information is supplied regarding outward forces and
objects. These are touch, taste, smell, seeing, and hearing, to
which may be added the muscular sense and a sense of temperature.

309. General Sensations. The body, as we have learned, is made up of
a great number of complicated organs, each doing its own part of the
general work required for the life and vigor of the human organism. These
organs should all work in harmony for the good of the whole. We must have
some means of knowing whether this harmony is maintained, and of receiving
timely warning if any organ fails to do its particular duty.

Such information is supplied by the common or general sensations.
Thus we have a feeling of hunger or thirst indicating the need of food,
and a feeling of discomfort when imperfectly clad, informing us of the
need of more clothing.

To these may b