SECTION XII 



THE INFLUENCE ON THE CIRCULATION OF 

 VARIATIONS IN THE TOTAL QUANTITY OF 



BLOOD 



PLETHORA AND HYDR^MIC PLETHORA 



THE effects of increasing the total volume of circulating fluid may 

 be studied by injecting several hundred cubic centimetres of defi- 



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250 



240- 



230 



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210 



200 



190 



180 



170 



160 



150- 



140- 



130- 



120 



110 



100 



90* 



80 



70 



60 



50- 



40 



30 



20 



10 







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FIG. 475. Effects of hydraemic plethora on the pressures in the carotid artery 

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

 (BAYLISS and STARLING.) 



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



brinated blood or normal saline fluid into a vein. In the latter fease, 

 since the blood is rendered more dilute, the condition is called hydras-' 

 mic plethora (Fig. 475). 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 



1129 



