294 RESPIRATION 



the vaso-motor centre, also associated with periodic discharges from 

 the respiratory centre, may be observed under certain conditions 

 e.g., when in an animal paralyzed by curara, and therefore unable to 

 breathe spontaneously, the artificial respiration is stopped for a time. 

 If such a dose of curara be given as will still permit slight spontaneous 

 respiration to go on, and both vagi be cut, it can be seen on stopping 

 the artificial respiration that the waves on the blood-pressure curve 

 are exactly synchronous with the slow respiratory movements. The 

 Traube-Hering waves sink in inspiration and rise in expiration. 



The fact that they have invariably a longer period than the 

 natural respiratory movements indicates that they are not concerned 

 in the production of the normal respiratory oscillations of arterial 

 pressure. Probably the reason why the Traube waves appear after 

 section of the vagi is the increased vigour of the slow respiratory 

 discharges, coupled with a hyperexcitability of the vaso-motor 

 centre, due to the long pauses in the aeration of the blood. In the 

 asphyxial rise of pressure in a curarized dog they are constantly 

 seen, and are often observed when the circulation in the medulla 





Fig. 131. Traube-Hering Waves as the Blood-Pressure is falling during Occlusion 

 of the Cerebral Arteries in a Cat. 



oblongata is in any way interfered with (Fig. 131). In addition to 

 the true Traube-Hering waves, other and much longer periodic 

 variations in the blood-pressure are sometimes noticed. If spon- 

 taneous respiration is going on, their long sweeping curves then show 

 the ordinary respiratory waves superposed on them. 



The normal respiratory oscillations in the veins, as might be 

 expected, run precisely in the opposite direction to those in the 

 arteries, and so do the Traube-Hering curves. The increased flow 

 from the veins to the thorax during inspiration lowers the pressure 

 in the jugular vein, while it increases the pressure in the carotid. 

 The constriction of the small bloodvessels to which the Traube- 

 Hering curves are due increases the blood-pressure in the arteries, 

 because it increases the peripheral resistance to the blood- flow; in 



