ons are alike. All the above questions can be safely and surely
answered in the light of science and experience combined, but such
questions cannot be settled by the dictum of any singer, teacher, or
writer, nor does the experience, in itself, of any one person furnish
an adequate guide for others.

[Illustration: FIG. 53. By this diagram the author has attempted to
give the reader some idea of the nature of the chain of processes
involved in singing a single tone, from the time the eye looks on the
note till the muscles concerned have given it utterance as a tone. The
various nervous centres concerned are all in the brain (though the
spinal cord supplies some subordinate centres). There are sensory
centres, or those for the eye and the ear, and motor centres, or those
sending the commands to the muscles involved. Further, these must be
_connected_ by paths not shown in detail, but represented by one
centre spoken of as an "association" centre, which may also, possibly,
have much to do with emotions, etc. But, at all events, the dependence
of movements on ingoing messages or sensations is emphasized. The deaf
cannot speak or sing, and the blind cannot read (ordinary) music. The
defect may not be in either senses or muscles, but in the relating
nervous mechanism between them. As explained in the body of the work,
execution depends on at least two factors, sensations, or ingoing
messages, and movements determined by these. Now the _connection_
between the ingoing and the outgoing impulses is the most important
and the least understood part, but the above diagram will at least
serve to emphasize the fact that such connections exist, and that in a
general way the result, performance, can be explained. No attempt has
been made to trace the path of other sensory impulses than those from
eye and ear, as this would make the diagram too complicated.]

Investigation has shown that the use of muscles tends to the
accumulation of the waste products of vital activity; that such
accumulation is associated with the experience in consciousness of
what we term "fatigue," and which is preceded by "weariness." The
latter is a warning that the more serious condition is approaching,
but is to be distinguished from another feeling not necessary to name,
often present in unwilling youthful students, and for which various
forms of treatment are sometimes tried so unsuccessfully that it is as
well to discontinue study altogether.

1. The tim