HISTORY OP THE REFLEX THEORY. 
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the perception of external sensations is removed by removal of 
the brain. Unzer thinks that the brain is the seat of the soul, 
and it is impossible for any other organ to have a sensation. 
Hence he remarks, “ a headless tortoise lives several months ; 
it cannot possibly feel the sensation of faintness from an empty 
stomach; yet the external impressions must change the vital 
movements contra-naturally like that painful sensation, because 
it becomes feeble and faint from starvation. The digestive 
organs must be excited to the movement, which are requisite 
to digestion, by the external impressions of emptiness, just as 
by the instinct, since the bowels are moved peristaltically and 
the digestive fluids are secreted.” 
Having thus proved, as he thinks, that many actions take 
place without sensation, because they take place without the 
brain, Unzer ascribes to a similar mechanism all those actions 
of which we are unconscious : in such cases the impressions on 
the sensitive nerve are not transmitted to the brain, but are 
deflected from their course, and excite the muscles, without 
having reached the brain. “ "What prevents the propagation 
to the brain?” he asks. “There is nothing to be found in the 
nerves adapted to this end, except certahi formations found 
scattered on the nerves, termed ganglia.” This conjecture 
may or may not be accepted, he says, “ still the fact remains, 
that external impressions on certain nerves excite movements 
without reaching the brain and without being felt.” Replace 
this hypothesis of the ganglia on the nerves, as the centres of 
deflection, by the hypothesis of the spinal centres, and the 
modern Reflex Theory is before you ; not indeed the theory of 
Marshall Hall, but that of his successors. 
Prochaska is the next name on our list. As far as my own 
investigations and meditations enable me to understand this 
complex subject, Prochaska seems most nearly to have ap- 
proached to a philosophical and systematic explanation, however 
erroneous some of his details may be. He alone, since Stahl, 
has seen the necessity of making all the nervous centres seats 
of sensation, and the brain the seat of ideation .* “ However 
composite the machine of the nervous system may be,” he says, 
“ I think it may be divided into three portions, just as its func- 
tions are most conveniently ranged under three divisions ; 
namely, in the first place, the animal organs (or the organs of 
the mental faculty), the cerebrum and cerebellum; secondly, 
* CiESALPiNus held this view : “ Ibi esse animse principatum uli origo est 
nervorum ; ” it is true that he, believing the heart to he that origin, imme- 
diately adds, “ Sed hoc cerebrum esse, non dicet nisi is qui crasse hrec con- 
templetur.” — Peripateticarum Qucestiones, 1571, p. 108. Whytt had arrived 
at the conclusion that the whole, and not a part, of the nervous system, was 
the seat of the mind ; hut he placed reason in the brain and sensation in 
the nerves. — (Works, p. 288 — note.) 
NO. II. 
P 
