The vacant expression of the eyes is very peculiar, and at once shows
when a man is completely lost in thought. Professor Donders has,
with his usual kindness, investigated this subject for me.
He has observed others in this condition, and has been himself observed
by Professor Engelmann. The eyes are not then fixed on any object,
and therefore not, as I had imagined, on some distant object.
The lines of vision of the two eyes even often become slightly divergent;
the divergence, if the head be held vertically, with the plane
of vision horizontal, amounting to an angle of 2'0 as a maximum.
This was ascertained by observing the crossed double image of a
distant object. When the head droops forward, as often occurs with a man
absorbed in thought, owing to the general relaxation of his muscles,
if the plane of vision be still horizontal, the eyes are necessarily
a little turned upwards, and then the divergence is as much as 3'0,
or 3'0 5': if the eyes are turned still more upwards, it amounts
to between 6'0 and 7'0. Professor Donders attributes this divergence
to the almost complete relaxation of certain muscles of the eyes,
which would be apt to follow from the mind being wholly absorbed.
Pages:
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339