NERVOUS CONTROL OF RESPIRATORY APPARATUS 199 



oblongata known as the respiratory center be removed, no 

 further respiratory movements will take place, and death 

 immediately follows. 

 On the other hand, the 

 whole of the brain for- 

 ward of the medulla 

 may be removed, and 

 breathing will not stop. 

 278". The Expiratory 

 Center. It is now un- 

 derstood that the cen- 

 ter of respiration in 

 the medulla is in real- 

 ity double, that there 

 is one center for inspir- 

 atory movement and 

 another beside it for 

 expiratory movement. 

 In ordinary quiet 

 breathing the first only 

 is excited, expiration 

 taking place by the re- 

 laxation of the muscles 

 contracted in inspira- 

 tion. But in violent or 

 forced expiration the 

 internal intercostal and 

 abdominal muscles are 

 brought into active use, 

 and the nervous influ- 

 ence stimulating them 

 to action comes from 

 the expiratory center. 



Fig. 107. Diagram of the nervous con- 

 trol of the respiratory organs. 



ab motor spinal nerves going to muscles of 

 the abdominal walls. 



E expiratory center. 



ex sensory nerve fibers from the larynx ex- 

 citing the expiratory center. 



ex' sensory fibers from the lungs exciting 

 the expiratory center. 



ext motor spinal nerve fibers passing to 

 external intercostal muscles. 



/ inspiratory center. 



in sensory fibers from larynx inhibiting 

 the inspiratory center. 



in' sensory fibers from the lungs that excite 

 the inspiratory center. 



int motor spinal nerve fibers passing to in- 

 ternal intercostal muscles, 

 motor fibers of phrenic nerve going to 

 diaphragm. 



ph 



