-half away from the
surface of the skin he feels it. Again at about three inches from this
point he feels the prick of the needle, but is insensible to it in the
space between these two points. Then there comes another interval in
which no sensation is conveyed, but at about three inches still further
away he again feels the sensation, and so on; so that he appears to be
surrounded by successive zones of sensation, the first about an
inch-and-a-half from the body, and the others at intervals of about
three inches each. The number of these zones seems to vary in different
cases, but in some there are as many as six or seven, thus giving a
radius of sensation, extending to more than twenty inches beyond the
body.

Now to explain this we must have recourse to what I have already said
about waves. The heart and the lungs are the two centres of automatic
rhythmic movement in the body, and each projects its own series of
vibrations into the etheric envelope. Those projected by the lungs are
estimated to be three times the length of those projected by the heart,
while those projected by the heart are three times as rapid as those
projected by the lungs. Consequently if the two sets of waves start
together the crest of every third wave of the rapid series of short
waves will coincide with the crest of one of the long waves of the
slower series, while the intermediate short waves will coincide with the
depression of one of the long waves. Now the effect of the crest of one
wave overtaking that of another going in the same direction, is to raise
the two together at that point into a single wave of greater amplitude
or height than the original waves had by themselves; if the reader has
the opportunity of studying the inflowing of waves on the seabeach he
can verify this for himself. Consequently when the more rapid etheric
waves overtake the slower ones they combine to form a larger wave, and
it is at these points that the zones of sensation occur. If the reader
will draw a diagram of two waved lines travelling along the same
horizontal line and so proportioned that the crest of each of the large
waves coincides with the crest of every third wave of the small ones, he
will see what I mean: and if he then recollects that the fall in the
larger waves neutralizes the rise in the smaller ones, and that because
this double series starts from the interior of the body the surface of
the body comes just at one of these neutralized points,