RESPIRATION 



271 



Traube-Hering waves sink in inspiration and rise in expira- 

 tion. 



The fact that they have invariably a longer period than the 

 natural respiratory movements indicates that they are not con- 

 cerned 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 hyper excitability 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 oblongata is in any way interfered with (Fig. 116). 

 In addition to the true Traube-Hering waves, other and much longer 

 periodic variations in the blood-pressure are sometimes noticed. 



FIG. 116. TRAUBE-HERING WAVES AS THE BLOOD-PRESSURE is FALLING DURING 

 OCCLUSION OF THE CEREBRAL ARTERIES IN A CAT. 



If spontaneous respiration is going on their long sweeping curves 

 then show the ordinary respiratory ^vvaves ^superposed on them.j 



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 the veins it lowers the pressure, because less blood 

 gets through to them. Accordingly, when the Traube-Hering 

 curve is ascending in the carotid, it is descending in the jugulai. 



The respiratory variations in the volume of the brain, 

 which are so striking a phenomenon when a trephine hole is 

 made in the skull, but which can also take place, thanks to the 



