CHAP. IL] RESPIRATION. 657 



the right side of the heart, for the total effect of all these move- 

 ments is to augment the flow along the veins to the heart. But 

 the pulmonary peripheral resistance still remaining excessive con- 

 tinues to hinder the progress to the left side, and hence the right 

 side becomes increasingly distended. 



388. During asphyxia, under urari, the blood-pressure curve 

 shews certain other interesting features deserving of attention. 



Upon the cessation of the artificial respiration, the respiratory 

 undulations of course cease also, so that the blood-pressure curve 

 rises at first steadily, being broken only by the heart-beats; yet after 

 a while new undulations, the so-called Traube or Traube-Hering 

 curves, make their appearance (Fig. 86, -2, 3), similar to the previous 

 ones, except that their curves though variable are as a rule larger 

 and of a more sweeping character. These new undulations, since 

 they appear in the absence of all thoracic or pulmonary move- 

 ments, passive or active, and are witnessed even when both vagi 

 are cut, must be of vaso-motorial origin ; the rhythmic rise must 

 be due to a rhythmic constriction of the small arteries, and this 

 probably is caused by a rhythmic discharge from vaso-motor centres, 

 and especially from the bulbar vaso-motor centre. The un- 

 dulations are maintained so long as the blood-pressure continues 

 to rise. With the increasing venosity of the blood, the vaso-motor 

 centres become enfeebled and the undulations disappear. 



We may here incidentally remark that the occurrence of such 

 long slow undulations of the blood-pressure is not dependent on the 

 cessation of the respiratory movements, and on an abnormally 

 venous condition of the blood. They are sometimes (Fig. 87) seen 



FIG. 87. BLOOD-PRESSURE CURVE OF A EABBIT, RECORDED ON A SLOWLY 



MOVING SURFACE, TO SHEW TRAUBE-HERING CURVES. 



(The curve was described not by means of a mercury manometer, but by an 

 instrument similar to but not identical with Fick's spring-kymograph.) 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 undulations 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. 



