918 



PHYSIOLOGY 



By taking the pressure at different parts of the circulation, we obtain 

 a distribution which is represented roughly in the accompanying diagram 

 (Fig. 386). The blood pressure, which is about 100 to 120 mm. Hg. in 

 the large arteries near the heart, falls only slowly in these arteries, so that 



Fid. 380. Scheme of blood pressure in A, the arteries; c, capillaries; and V, veins. 



oo, line of no pressure; LV, left ventricle; RA, right auricle; BP, height of 



blood pressure. 



in the radial artery it is not very much below that in the aorta. Between 

 the medium-sized arteries and capillaries there is a very extensive fall of 

 pressure as the blood passes through the arterioles, so that in the capillaries 

 the pressure on an average may be taken as 20 to 40 mm. Hg; from the 

 capillaries to the veins the blood pressure falls steadily until in the big 

 veins near the heart it may be negative. 



