SECTION XII 



THE INFLUENCE ON THE CIRCULATION OF VARIATIONS 

 IN THE TOTAL QUANTITY OF BLOOD 



PLETHORA AND HYDR/EMIC PLETHORA 



THE effects of increasing the total volume of circulating fluid may be studied 

 by injecting several hundred cubic centimetres of defibrinated blood or 

 normal saline fluid into a vein. In the latter case, since the blood is rendered 



JO 60 SEC 



IMIN? 344 5 6 7 8 9 JO II 12 13 14 15 16 17 18 21 22 



FIG. 474. Effects of hydrsemic plethora on the pressures in the carotid artery (thick 

 line), portal vein (thin line), and inferior vena cava (dotted line). (BAYLiss and 

 STABLING.) 



The arterial pressure is in mm. Hg. ; the venous pressures in mm. H 2 0. 



more dilute, the condition is called hydrsemic plethora (Fig. 474). On the 

 arterial pressure the result of such an injection is not very marked. There is 

 a slight initial increase in the pressure, but the increase is by no means 

 proportional to the amount of fluid injected, showing that the fluid is not 

 to any large extent contained in the arterial system. On examining the 

 pressure in the veins, however, we find a very great relative rise of pressure, 



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