SUMMARY. REFLEX MOVEMENTS. 303 



the performance of complex, though habitual, movements on musical 

 instruments ; other habitual, and all the instinctive movements of men 

 and animals; and, as the results of morbid or exalted action, the roll- 

 ing of the eyeball and spasm of the eyelids, in irritable states of the 

 retina, and the spasmodic movements of hydrophobia, hysteria, chorea, 

 epilepsy, and tetanus. In the sphere of vegetative life, may further be 

 mentioned, the action of the cardiac, and perhaps of the pyloric, cir- 

 cular fibres of the stomach ; and certain general movements of the 

 stomach and intestines; yawning, and sighing, as the results of fatigue, 

 or of some oppression of the respiratory organs ; and even laughter, 

 when caused by tickling, and not by ludicrous ideas, or pleasurable 

 emotions. 



The office of the great excitable nervous centre of the reflex actions 

 may be said generally to be to excite and regulate all the muscular 

 movements necessary for the continuance of organic or vegetative life. 

 It has' been well remarked that it never sleeps. (Marshall Hall.) 

 Whilst various movements, immediately necessary for the preservation 

 of the organs, or of life itself, are thus performed, those which, like 

 the prehension of food and others, are only more remotely necessary, 

 have more or less of reason and will associated with them. In this latter 

 case the afferent impressions from without ascend to the cerebrum and 

 operate by inducing ideas, emotions, reasoning processes, and volition ; 

 and this is the ordinary case with man. If, however, their ascent to 

 the cerebrum be arrested by sleep, coma, the influence of narcotics, or 

 the actual destruction of the parts by disease ; or even if the powers of 

 the attention be not directed to them, then purely sensori-motor actions 

 ensue, as is the normal case in those of the lower animals which possess 

 no higher nervous centres than these sensory ganglia. Extremely 

 powerful stimulation of these parts in man is also followed by sensori- 

 motor acts, even when the cerebral functions are in a state of perfect 

 activity. The actions of infants generally exhibit the same absence of 

 cerebral government, being mostly sensori-motor, as, for example, the 

 act of sucking. Lastly, in idiots the predominance of the sensori-motor 

 over the rational acts is very obvious. 



The particular parts of the great excitable centre which are called 

 into action in these several reflex movements, may be inferred from 

 the attachments of the afferent and efferent nerves engaged; that is to 

 say, of the afferent nerves which receive the external stimulus and 

 convey its effects to the nervous centre, and of the efferent nerves which 

 supply the muscles thrown into action. These details will be referred 

 to under the description of the functions of the several organs concerned 

 in these reflex movements. 



The involuntary reflex movements whether complicated or simple in 

 their nature, require no previous education or instruction for their 

 proper performance ; and thus their due occurrence is provided for in- 

 dependently of any effort of the intelligence and the will, so that the 

 mind is free to perform its own workings, whilst the care of the body 

 is intrusted to other powers resident in the system which induce no 

 exhaustion of the volitional power. Nevertheless some of these reflex 

 movements, whether ideational, emotional, instinctive, or simply pre- 



