304 SPECIAL PHYSIOLOGY. 



servative, may be controlled by the will, and may also be imitated under 

 the influence of the will ; for we may stop laughter or sobbing, or arrest 

 for a time the respiratory movement; or, on the other hand, we may 

 imitate or perform these movements through voluntary efforts. A 

 certain number of these movements, however, are placed entirely be- 

 yond the direct control of the will, as the movements of the iris and 

 the last stage of deglutition. 



The higher reflex movements, viz., the ideational and emotional are 

 ordinarily accompanied by consciousness and sensation ; but ideas oc- 

 curring in dreaming and like states of unconsciousness also give rise to 

 similar movements, which therefore furnish examples of cerebral reflex 

 acts without conscious sensation. The other reflex movements may 

 also be accompanied by sensation, as, for example, the act of degluti- 

 tion, the- acts of coughing and sneezing, and that of snatching away 

 the hand from a hot body. But the lower reflex movements, whether 

 complex or simple, are not necessarily attended with conscious sensa- 

 tion, and are certainly quite independent of it, as we see in the move- 

 ments of the iris; also in instances of paralysis of the lower limbs, in 

 which the reflex movements still continue ; and likewise in the perform- 

 ance of deglutition, and of respiration in a state of profound coma, and 

 of respiration under the influence of chloroform, or in the condition of 

 sleep, both of which have the effect of perfectly suspending conscious 

 sensation. This independence of sensation on the part of the reflex 

 acts necessarily diminishes the fatigue that would be attendant upon 

 their performance if they were incessantly brought before the mind as 

 subjects of the faculty of attention. 



There are certain movements, performed by man, and animals, which 

 are known as automatic ; examples of these are met with not only in 

 the involuntary but also in the voluntary muscular organs. The 

 rhythmic movements of the heart are of this kind, and also those of 

 respiration. But besides this, certain instinctive acts, and even the 

 simpler or habitual acts of locomotion, have been regarded as auto- 

 matic, or as simple reflex movements, performed without the agency 

 of the will. In the cold-blooded vertebrata, and still more obviously 

 in insects and myriapods, for example, simple progressive locomotion 

 appears to be almost or entirely independent of volition ; for decapi- 

 tated centipedes will, if stimulated, run rapidly forward, will even 

 raise their headless trunks over small obstacles, and force them per- 

 sistently against more formidable ones ; decapitated lizards exhibit 

 similar, though less prolonged, movements. In the habitual move- 

 ments of walking performed by ourselves, volition, and sometimes 

 even consciousness, take but little or no part; and thus they become 

 truly automatic. Many persons, moreover, as, e. g., orators, actors, 

 musicians, and particular handicraftsmen, acquire by habit, or neces- 

 sity, the power of performing very special movements, without the 

 continued aid of volition ; such movements have been named second- 

 arily automatic, and have been supposed to be accomplished through 

 the sensori-motor, or even through the purely excito-motor, nervous 

 centres. They are, indeed, reflex actions of a higher order than the 

 reflex movements natural to every one, and might be termed acquired 



