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3 6 4
RECENT TIMES.
the force in question to be attended with chemical changes
in the nerve-contents. Those who were dissatisfied with j
both explanations, had recourse to the hypothetical " vital
spirits," which gave the wished-for answer to all questions. |
The brain was generally accepted as the centre of intellectual
activity. WILLIS ventured even to localize the |
different psychical faculties in particular parts of the brain; ,
thus he seated sensation in the corpora striata, memory in /
the medullary substance, and the animal functions in the . |
cerebellum. R. WHYTT came to the conclusion after J
numerous vivisections that the capacity for movement is
preserved for some time after death, and referred to the fact
that decapitated frogs " move in a co-ordinated manner,
and, as it were, with intelligence." He concluded from
this that the brain cannot be the only centre of ^
intellectual activity* CALDANI made attempts to j
investigate the physiological functions of the spinal cord,
and with this object destroyed different parts of it.
The great astronomer KEPLER drew the outlines of a
correct theory of vision, remarked upon the difference in
the curvatures of the anterior and posterior surfaces of the ]
lens, explained that this organ is by no means the seat of
vision, as had hitherto been thought, but serves the purposefj
of refracting the incident rays of light into the direction
required. He followed the course of these rays until they
impinge upon the retina,t and pointed out that myopia and j
hypermetropia depend upon abnormalities in the refracting
media, and that with suitable spectacles, fitted with concave
or convex glasses, a correct image of an object is produced.
Father SCHEINER, of Vienna, completed these investigations,
and showed by the experiment named after him that
an object is only clearly seen when removed to a certain
definite distance from the eye. He at the same time
* ROB. WHYTT : An essay on the vital and involuntary motions cf animals,>i
Edinburgh 1751, p. 344 f t seq., 384 et seq.— R. WHYTT : Physiological essays,
Edinburgh 1755, p. 107 et seq.-, 214 et seq.
t POGGENDORFF op. cit., S. 168 et stq.