382 
CONSENSUAL ACTIONS IN MAN. 
The insect will in fact appear to the fish a little above the 
place which it really occupies ; and the difference is not con¬ 
stant, hut varies with every change in the relative positions 
of the fish and the insect. Yet the wonderful instinct with 
which the fish is endowed, leads it to make the due allowance 
in every case; doing that at once, for which a long course of 
experience would be required by the most skilful Human 
marksman, under similar circumstances. 
477. Though the Intelligence and Will of Man in a great 
degree supersede his consensual impulses, in the same man¬ 
ner as they hold in subordination his reflex movements 
(§ 471), yet we have many indications of the direct operation 
of sensations in determining respondent movements. Of this 
kind are the start produced by a loud sound, particularly if 
unexpected; the closure of the eyes to a dazzling light, or on 
the sudden approach of a body that might injure them; the 
production of sneezing by a dazzling light; the provocation 
of laughter by tickling, or by some sight or sound to which 
no distinct ludicrous idea or emotion attaches itself; and the 
excitement of vomiting by highly disagreeable sensations, as 
the sight of a loathsome object, an offensive smell, a nauseous 
taste, or by tickling the back of the mouth with a feather. 1 
Hone of these “ consensual ” movements can be excited with¬ 
out the consciousness of the subject of them; and this 
circumstance marks them out as belonging to a different 
category from the “reflex” movements performed through 
the instrumentality of the Spinal Cord.—In some convulsive 
disorders, the attacks are excited by causes that act through 
the organs of sense : thus, in Hydrophobia we observe the 
immediate influence of the sight or sound of liquids; and in 
many Hysteric subjects, the sight of a paroxysm in another 
individual is the most certain means of its induction in them¬ 
selves. 
478. But we may trace the agency of the Sensory Ganglia 
1 This is the most ready way of exciting vomiting, when it is desired 
to free the stomach from poisons or unwholesome articles of food; 
but care must be taken not to apply the feather so low down as to 
cause it to be grasped by the muscles concerned in the act of swallow¬ 
ing ; for its irritation, instead of producing vomiting, will then occasion 
an act of deglutition (§ 195), which may draw the feather from the 
hand of the operator, and carry it down into the stomach of the 
patient. 
