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profoundly saw tliat tlie mind does not always reflect upon its 
acts ; some of its most indubitable acts are performed uncon- 
sciously.* This conception of the soul as tantamount to both 
mind and vital principle still finds ardent advocates; and this 
very year an eminent professor (Tissot) has published a thick 
volume (“ La Vie dans P Homme ”) which may be called an 
amplification of Stahl’s hypothesis. 
But we are seeking the organic mechanism, and these hypo- 
theses will not assist us. The dawn of the discovery is in 
[Inzer’s celebrated work, which the “ Sydenham Society” has 
made generally accessible, through Dr. Laycock’s translation. f 
Unzer not only collected a mass of interesting facts relative to 
the actions of the nervous system, but discriminated them with 
great precision, and attempted to determine then mechanism. 
He classed all the phenomena under the two heads of sentient 
actions ( actio lies anhno), and nerve-actions — the latter being 
wholly independent of sensation. 
It is true that the only proof of their being independent of 
sensation is that they may be seen in brainless animals; which, 
as I have elsewhere shown, is no proof at all. J “ Thus,” he 
says, “a decapitated animal will stand, move forwards, raise 
itself up, leap, fly, flutter its wings, seek food, clean, defend or 
conceal itself, &c. A decapitated man, immediately after de- 
capitation, struggles to free his hands, attempts to stand up- 
right, and to stamp with his feet. If the head of a pigeon be 
cut off’ whilst it is running, it continues to run on for some dis- 
tance until it knocks against something ; a frog leaps forward 
without its head ; a snake, a fish, a worm, writhes and twists 
about, if touched, although wholly deprived of sensation ; a fly 
makes a movement of brushing its eyes by a natural instinct, 
although its head be cut off ; a headless snail seeks its food by 
its usual plan of feeling about ; a decapitated tortoise does the 
same thing-, and will live for half a year after decapitation, and 
raise itself up, or endeavour to do so, if placed on its 
back ; an earwig nips with the nippers of his abdomen at 
its own separated head, when the head bites the abdomen ; 
in short, all the instinctive actions of animals are some- 
times seen to occur as nerve actions; and it naturally follows 
that they occur as such, at first in newly-born animals, and 
that it is only after the perception of external sensations that 
they become sentient actions.” Here we perceive that the 
reason why these actions are excluded from sensation is because 
* Stahl : De Mechanismi et Orgcmismi Diversitate. 
t Unzer : The. Principles of Physiology. Prochaska : A 'Dissertation on 
the Functions of the Nervous System. Translated by Thomas Laycock, M.D. 
t The Reflex Theory, and the evidence on which it is based, are fully 
discussed in the “ Physiology of Common Life,” vol. ii. 
