HISTORY OF THE REFLEX THEORY. 
197 
without the brain as with it ; and even when the brain is 
present, and uninjured, these actions mostly take place without 
exciting any sensation. How is this ? 
Aristotle, and the earlier physiologists, made short and easy 
work of it. According to them the soul moved the body, and 
every action was due to an impulse of the soul ; how the motion 
was effected no one attempted to explain. As, however, 
it appeared that the mind was not conscious of some of these 
impulses, the hypothesis was formed of three different souls 
or three forms of the one soul (the rational, the sentient, and 
the vegetative), which severally presided over the functions of 
intelligence, volition, and nutrition. This hypothesis was 
deemed so satisfactory that it reigned undisturbed until the 
middle of the seventeenth century. To the modern physio- 
logist, it seems nothing but a re-statement of the original 
difficulty : it gives a name to the cause of the phenomena of 
growth, volition, and intelligence, but in no sense does it 
explain the phenomena — in no sense does it unveil the cause. 
Indeed, the mechanism of nervous phenomena was scarcely 
suspected at this period. 
Our own Willis was the first to sketch this mechanism. His 
exposition of the nervous system, in man and animals, made an 
epoch ; and although his physiology is encumbered with 
“ animal spirits,'’' 1 “ subtle atoms,” “ flames/’ and other super- 
stitions of his day, it is a great advance on what had previously 
been taught. The problem we have at present before us he 
solved by the hypothesis of two souls — one, the amnia, or sen- 
sitive, corporeal, igneous sord of brutes, which presides over all 
the organic processes, as well as over all instincts, emotions, and 
involuntary acts ; and another, the animus, or rational, im- 
material, immortal soul, which is the exclusive appanage of man ; 
the animci man shares with brutes, the animus is his peculiar 
prerogative. It would lead me too far to detail the anatomical 
mechanism which Willis has assigned for the functions of these 
souls, or his attempt to localize perception in the corpora 
stricta, imagination and appetite in the corpus callosum, and 
memory in the convolutions of the cerebrum ; * enough for the 
present to indicate that he made the nervous system the in- 
strument of the rational soul, and the body, so to speak, of the 
sensitive soul. 
Stahl, less of an anatomist, and more of a metaphysician, ad- 
mitted but one soul — the rational. To it he assigned all the 
actions of the body. As to the obvious objection that the soul 
was quite unconscious of many impulses necessary to organic 
life, he replied that this was quite consistent with his view. He 
* dee particularly De Animal Brutorum, i. cap. iv. (Opera, eel. 1676, 
vol. ii. p. 36.) 
