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TEXT-BOOK OF PHYSIOLOGY 



maintain the normal rate and extent of the inspiratory discharge. The 

 stimulus to the development of these nerve impulses is generally believed 

 to be the distension of the air cells at the beginning of the inspiratory 

 movement. 



Moreover, if the central end of the divided superior laryngeal nerve be 

 stimulated with induced electric currents, the foregoing effect is increased, 



FIG. 195. DIAGRAM SHOWING THE RELATION OF THE PULMONIC FIBERS OF THE VAGUS TO 

 THE INSPIRATORY CENTER AND THE CONNECTIONS OF THE LATTER WITH THE PHRENIC AND 

 INTERCOSTAL NERVE CENTERS AND THEIR RELATED MUSCLES. (G. Bachmann.) med. ob. Medulla 

 oblongata. sp. c. Spinal cord. p.v. r. Pulmonic vagus nerve, excitator and inhibitor, insp. c. 

 Inspiratory center, phr. c. Phrenic nerve-centers, phr. n. Phrenic nerve, int. n. c. Intercostal 

 nerve-centers, int. c. n. Intercostal nerves, ext. int. c. m. External intercostal muscles. 



viz.: a further inhibition of the inspiratory center and consequently a 

 further decrease in the extent of the inspiratory and an increase in the ex- 

 tent of the expiratory movement until the inspiratory muscles pass into the 

 state of relaxation and the thoracic walls come to rest in the condition of com- 

 plete expiration. This would indicate that the superior laryngeal nerve 

 contains nerve-fibers which are capable, when sufficiently stimulated of 

 inhibiting the activity of the inspiratory center, and therefore the extent of 



