300 



MANUAL OF PHYSIOLOGY. 



eral idea of the average permanent differences that exist in the 

 different vessels of large animals and man. 



Large arteries (Carotid, Horse) + 160 mm., mercury. 

 Medium " (Brachial, Man) -f 120 mm., " 

 Capillaries of Finger, -\- 38 mm.. ' 



Small Veins of Arm, + 9 mm., " 



Large Vein of Neck, I to 3 mm., u 



If the different parts ot the circulation be represented on the 

 FIG. 134. 



l>iagram showing the relative height of the blood pressure in the different regions of 

 the vessels. H. Heart. A. Arteries, a. Arterioles. c. Capillaries, v. Small veins. 

 v. Large veins. H. v. being the zero line, the pressure is indicated by the elevation of 

 the curve. The numbers on the left give the pressure (approximately) in mm. of mer- 

 cury. 



base line H. A. c. v., these letters corresponding to heart, arteries, 

 capillaries and veins respectively, and if the height, of the blood 

 pressure be represented on the vertical line in mm. Hg, the curve 

 h, a, c, v, would give about the relative pressure in the various 

 parts of the circulation. This shows that in the receiving chamber 

 of the heart the pressure is below zero, while the ventricular pump 

 drives it to the height of the arterial pressure 160 mm. Hg. Iii 



