620 



INFLUENCE OF VAGUS NERVES. [BOOK n. 



either not materially changed, or if affected becomes slower 



(Fig. 77). If both be divided (Fig. 78) it becomes very slow, 



the pauses between expiration and inspiration being markedly 



prolonged. The character of the respiratory movement too is 



FIG. 78. EFFECT ON RESPIRATION OF SECTION OF BOTH VAGUS NERVES. 



The curve was obtained in the same way as Fig. 77. The second vagus nerve 

 was divided at x. 



markedly changed ; each respiration is fuller and deeper, so much 

 so indeed that, according to some observers, what is lost in rate 

 is gained in extent, the amount of carbonic acid produced and 

 oxygen consumed in a given period remaining after division of 

 the nerves about the same as when these were intact ; but it is 

 undesirable to insist too much on the exactness of this compen- 

 sation. 



When after division of both vagus nerves in the neck, the 

 bulb being intact, the central stump, that connected with the 

 central nervous system, of one of them is stimulated with a gentle 

 interrupted current, the effects are not always the same ; one 



FIG. 79. QUICKENING OF RESPIRATION BY GENTLE STIMULATION OF THE CENTRAL 

 END OF THE VAGUS TRUNK. 



The curve was obtained in the same way as Figs. 77, 78. Stimulation of the 

 vagus began at x, and ended at y. 



