y my conjectures.
The master who had been so conscientious in making her hold the bow
in this strained and ungainly position was blessed with an abnormally
long thumb; the pupil's thumb was short. What came natural to the one
was a strain on the other.

The function of the thumb is that of a pivot; a fulcrum. The bow is a
lever resting thereon, and its pressure on the string is regulated by
the first and second fingers on the one side and by the third and
fourth on the other. It would thus appear that the best place for the
thumb would be exactly between the second and third fingers. But it
is not given to every thumb to drop _naturally_ into this position.
And here is to be noted the germ of facility in bowing. Every thumb
closes naturally on a certain spot; it may be on the second finger,
or on the third. If the former it can be made to rest on the third or
even the fourth without apparent effort, but minute observation will
detect an infinitesimal strain when the thumb is taken beyond its
natural resting place. Therefore I maintain that the best position
for the thumb is to be determined by examination of the hand and
thumb, and will differ slightly in each individual player. It is
curious to note how many teachers, some of extreme eminence, take
such pains to perpetuate their own bad habits in their pupils under
the impression that they are teaching a perfect and superior
technique. I am afraid that it sounds somewhat of a heresy to speak
of great players and teachers having "bad habits"; the expression is,
perhaps, rather strong, but what I refer to is the "personal
equation." Such a player has a tendency to part his fingers, another
elevates the fourth finger in certain passages, this one has a
peculiar movement of the elbow, etc., etc. All these divergencies
from rigid and pedantic technique being the result of their several
physical differences. When these men prove themselves great artists
and attain high positions as teachers their advice is sought on
matters of technique. Finding themselves oracles they first consult
the oracle by aid of looking glasses, analyse in this way their own
actions, and then the one who parts his fingers lays it down as a law
that the fingers should be parted, and the one with the peculiar
movement of the elbow will not rest until all his pupils have
acquired the same eccentricity. I will quote another example of this
sort of thing that came under my own observation some years ago.