374 



EFFECTS ON CIRCULATION. 



[BOOK ii. 



been suggested that the normal respiratory undulations may be due 

 to a rhythmic rise and fall of the activity of the vaso-motor centre, 

 synchronous, like that of cardio-inhibitory centre, with the respi- 



Fio. 62. BLOOD-PRESSUBE CURVE OF A BABBIT, RECORDED ON A SLOWLY MOVING 



SURFACE, TO SHEW TRAUBE-HERING CURVES. 



In each heart-beat the upward and downward stroke are very close 

 together but may be easily distinguished by the help of a lens. The undula- 

 tions of the next order are those of respiration. The wider sweeps are the 

 Traube-Hering curves, of which two complete curves and portions of two others are 

 shewn. Each Traube-Hering curve comprises about nine respiratory curves, and 

 each respiratory curve about the same number of heart-beats. 



ratory movements. A review of all the evidence however goes to 

 shew that the respiratory variations in blood-pressure are due to 

 the mechanical conditions discussed above, and that vaso-motor 

 influences intervene but little if at all. 



