REFLEX AND INSTINCTIVE ACTIONS. 
525 
of power to use them aright), is to study the particular defect 
under which the individual suffers; and then to make him 
practise systematically the various movements concerned in 
the production of the sounds in question, at first separately, 
and afterwards in combination, until he feels that his volun¬ 
tary control over them is complete. 
CHAPTER XIY. 
OF INSTINCT AND INTELLIGENCE. 
692. It will be remembered that, when the ISTervous System 
was described (Chap, xi.), it was shown to be the instrument 
of three classes of operations, each of which seems to be per¬ 
formed by a distinct portion of the apparatus.—I. The first of 
these is the class of simply Reflex actions, which are executed 
only in respondence or answer to impressions made upon the 
nerves proceeding to a ganglionic centre ; as when a Dytiscus, 
whose head has been cut off, executes swimming movements 
immediately that its feet come in contact with water. These 
movements evidently take place without any choice or direc¬ 
tion on the part of the animal, which, in executing them, 
seems like a mere machine adapted to perform certain actions 
when certain springs are touched; and it has been shown 
that they may be called-forth even without its consciousness. 
Of these reflex movements, the Spinal Cord of Vertebrata, and 
in Invertebrata the ganglia corresponding to it (in regard to 
their connexions with the organs of locomotion, respiration, 
&c.), are the instruments.—II. The second class comprehends 
those Instinctive actions, which differ from the preceding in 
being dependent on the sensations received by the animal, 
and in being, therefore, never performed without its conscious¬ 
ness. nevertheless, the animal in executing them is not 
guided by any perception of the object to be attained, or by 
any choice of the means by which it is to be accomplished; 
but acts blindly and involuntarily, in accordance with an 
irresistible impulse, implanted in it by its Creator for the 
purpose of causing it to do that, without or even against its 
Will, which it would not have chosen or devised by its very 
imperfect intelligence. The actions of this class are most 
