312 NERVOUS SYSTEM. 



flex movements, as the closing of the eyelids when the cor 

 nea is touched. True reflex movements may be produced 

 by carefully-executed experiments upon persons asleep. 

 We cannot arrest the act of vomiting induced by titillation 

 of the fauces ; and other instances of this kind might be 

 cited. 



Most of the true involuntary movements are reflex ; but 

 these have been or will be considered under their proper 

 heads. The movements of deglutition depend upon an im- 

 pression made upon the mucous membrane of the pharynx, 

 etc. The movements of respiration are excited by an impres- 

 sion made upon the general sensory nerves, due to want of 

 oxygen, as we have shown in treating of respiration. The 

 ejaculation of semen is also reflex. Important reflex actions 

 take place through the sympathetic nerves, such as the 

 movements of the intestines, vaso-motor movements, etc. ; 

 but these will be considered fully under the head of the 

 sympathetic system. Secretion, the action of the heart, 

 the contractions of the uterus, the action of the sphincters, 

 the movements of the iris, etc., take place through the sym- 

 pathetic and the cerebro-spinal system. 



As regards the farther action of the cord as a nerve-centre, 

 there are undoubtedly many functions influenced more or 

 less by this portion of the cerebro-spinal axis ; but these have 

 been treated of under their appropriate heads, or will be con- 

 sidered hereafter. 



