PASSAGE OF FOOD FROM MOUTH TO STOMACH 765 



be drawn into the lungs or driven into the nasal cavities. Such 

 an accident is prevented by the fact that every act of swallowing 

 inhibits a respiratory movement. This inhibition is effected reflexly 

 through the glossopharyngeal nerve. Stimulation of the central 

 end of this nerve at once causes cessation of respiration in whatever 

 phase it may happen to be (Fig. 333). This cessation lasts for five or 

 six seconds, i.e. a sufficient length of time for a whole series of acts 

 of deglutition. Respiration then recommences, and the inhibition 

 cannot be prolonged by continuing the stimulation of the glosso- 

 pharyngeal nerve. This inhibition of the activity of the respiratory 

 centre can be shown on oneself. If the breath be held until the 

 feeling of dyspnoea, i.e. the need to breathe, becomes insistent, relief 

 is at once experienced by swallowing, and the feeling of relief will 

 last for three or four seconds. 



