BIXX)D E'RI 12 : 



should take. Thej indicate thai our I 



mean blood pressure, h<>\\ it is maintain) 



vary. After we have learned tl then ; 



particular examination of the mechanism oi pump thai 



heartbeat; then finally we may pi < amine tl 



pro by which the caliber of tl mtrolled 



THE MEAN ARTERIAL BLOOD PRESSURE 



The firsl prerequisite to the investigation i b! 1 pn 



any other physical problem, is that ould p< by 



which it can be quantitatively measured. The eai 

 plish this was made by the English scientist, th< !.'• 

 little over a century after Harvey published his accoui I 



tinii of the hi I Hales connected a glass tube ni • in length ■■ 



vered artery of a Inns.-, the '•"in tion I two being m 



by means "t' a piece of brass pipe joined t" tin- windpipe 

 substitute for rubber tubing. He Pound on untying the lig I 



Py that tin- hi 1 P08e in tin- tube to a hri-_ r '' ' 



inches above the level <>t' the lefl ventricle "t" the heart, and thai 

 at full heigh 1 it rose ami fell with each pulse through a <li-' 

 three or four inchi - 



Mercury Manometer Tracin 



l • somewhal crude bul very significant experiment oi I! rly 



iilish.'d tin- existence of tin- enormous pressure al which th< 

 made t.. circulate through the arteries. To r< 

 investigation <>t' the factors on which this preat 

 r> to invenl some mi nvenient mei 



hut this was nut a mplished until a centurj lat.T, when l 



plied the er, which Ludwig subsequei 



that tracings mighl he taken (Pig 21 



I laving h a tracii sho\i n in l ' g 22, 



hnw it nia\ I I in the Btud} "t" blood !• ! 



must do is t" im BMure the a> erage licighl 



-ure: the mean art ''1 1 • 



distance multiplied bj i\\<>. because the distanci 

 eury lias moved up in 'lie limb "f the manoi 

 ing point is onlj 



boul 13 5 t imes hea^ ier than nn e< 

 measuremenl mi multiplied i 



