302 SPECIAL PHYSIOLOGY. 



The emotional movements, such as the sobbing of grief, or the smile 

 of joy, must likewise have the cerebral hemispheres as their centres of 

 origin, if we regard those hemispheres as the seats of the emotional 

 faculties themselves ; and not, as some imagine, the ganglia at the base 

 of the brain. 



The instinctive or sensori-motor movements, such as those of suck- 

 ing, clinging, or attempting to retain the balance, winking the eyes, 

 and many others, manifested even in the new-born infant, appear to 

 have their seat in the great centre of sensorial and motorial excitabil- 

 ity, extending from the corpora striata, optic thalami, and corpora 

 quadrigemina, through the cerebral peduncles, the pons and medulla, 

 and down through the whole length of the spinal cord; for such move- 

 ments continue after the cerebral hemispheres have been removed, in 

 animals, and occur in the human infant, in cases of monstrosity, in 

 which the upper part of the hemispheres is wanting. These instinctive 

 movements merely differ from the ordinary reflex acts, in being asso- 

 ciated with sensation, in being more complex, and in involving a 

 greater extent of the nervous and muscular apparatus. 



The simpler reflex, or excito-motor acts are also performed through 

 the agency of the same motorial gray centre, extending from the cor- 

 pora quadrigemina down to the lower end of the cord ; but they involve, 

 in their performance, smaller portions of that long chain of gray 

 nervous substance, and do not necessarily excite its sensorial portions. 



Of the reflex movements generally, whether excito-motor or sensori- 

 motor, some are concerned in regulating the functions of the organs 

 of the senses, such, as those which govern the condition of the iris, the 

 ciliary muscle, and the muscles of the tympanum. The preservative 

 reflex movements are illustrated by the winking of the eyelids to moisten 

 the eyeballs, and relieve the retinae temporarily from the effects of 

 light ; and by the acts of sneezing excited by impressions on the 

 retina, or on the nasal mucous membrane, for the expulsion of noxious 

 matter from the nose, of coughing to expel foreign bodies, or mucus, 

 from the larynx, or air-tubes, and of vomiting, whether induced by 

 disagreeable odors, tastes, or offending matters in the stomach, or even 

 by sea-sickness. The shutting of the eyelids and the closure of the 

 glottis, or aperture leading into the air-passages, for the prevention 

 of foreign bodies entering the eye, or of poisonous gases entering the 

 lungs are further illustrations of protective or conservative reflex 

 acts. 



The act of deglutition, and the respiratory movements, are also 

 reflex ; and so are the irregular or spasmodic inspiratory movements 

 produced by sudden application of cold water to the skin. Still more 

 simple spinal reflex movements are, the snatching away of the hand, 

 or the sudden lifting up of the feet, from unexpected causes of irrita- 

 tion. Many other illustrations may also be adduced of such reflex 

 movements ; such are, for example, belonging to muscles of animal 

 life the starting on hearing sudden, loud noises, probably also the 

 movements of walking in sleep, or in the state of somnambulism, though 

 these imply also a great power of co-ordination; even, to a certain 

 degree, the ordinary unconscious walk of persons absorbed in thought ; 



