394 



COMPARATIVE PHTSIOLOaY. 



Brain above medulla from which 

 Impulses modifying respiration 

 may proceed. 



'acial muscles. 



Respiratory centre 

 ill the medvllu. 



Cutaneous surface from which 

 afferent impiUses proceed di., 

 recfly to prain. 



Thoracic resp. muscles. 



Spinal cord.— p- 



Respiratory tract. 



Diaphragm with 

 phrenic nerve. 



Cutaneous sur- 

 face from which 

 impulses reach res- 

 piratory centre by 

 spinal cord. 



Fig. 309. — ^Diagram intended to illustrate nervous mechanism of respiration. Arrows 

 indicate course of impulses. 



