226 RESPIRATION. 



the will. For were it not so, it would be impossible to 

 perform those voluntary respiratory acts which have been 

 just enumerated and explained, as speaking, singing, 

 straining, and the like. 



The respiratory movements and their regular rhythm, 

 so far as they are involuntary and independent of con- 

 sciousness (as on all ordinary occasions they are), seem to 

 be under the absolute governance of the medulla oblon- 

 gata, which, as a nervous centre, receives the impression 

 of the "necessity of breathing," and reflects it to th& 

 phrenic and such other motor nerves as will bring into 

 co-ordinate and adapted action the muscles necessary to 

 inspiration. 



In the cases of voluntary respiratory acts, we may 

 believe that the brain, as well as the medulla oblongata, 

 is engaged in the process ; for we have no evidence of the 

 mind exercising either perception or will through any 

 other organ than the brain. But even when the brain 

 is thus in action, it appears to be the medulla oblongata 

 which combines the several respiratory muscles to act 

 together. In such acts, for example as those of cough- 

 ing and sneezing, the mind first perceives the irritation at 

 the larynx or nose, and may exercise a certain degree of 

 will in determining the actions, as e.g., in the taking of 

 the deep inspiration w r hich always precedes them. But the 

 mode in which the acts are performed, and the combi- 

 nation of muscles to effect them, are determined by the- 

 medulla oblongata, independently of the will, and have 

 the peculiar character of reflex involuntary movements, in 

 being always, and without practice or experience, precisely 

 adapted to the end or purpose. 



In these, and in all the other extraordinary respiratory 

 actions, such as are seen in dyspnoea, or in straining, 

 yawning, hiccough, and others, the medulla oblongata 

 brings into adapted combination of action many other 

 muscles besides those commonly exerted in respiration. 



