Carpenter's principles of human physiology . he resistance to the discharge of the blood from them ; Fig. 145. ^ VUa/^ ^ Fig. 146. and it falls when they dilate, because then the blood traverses them more it rises on exposure of the body to cold, which contracts the capillaries,and falls in a warm tempera-ture, which leads to the dilata-tion of the capillaries, and thisshows too that local variationsin the contraction of the ves-sels influence the pressure ofthe blood in the rest of thesystem. Constriction of a par-ticular artery causes diminishedflow through the artery itself,inc
Carpenter's principles of human physiology . he resistance to the discharge of the blood from them ; Fig. 145. ^ VUa/^ ^ Fig. 146. and it falls when they dilate, because then the blood traverses them more it rises on exposure of the body to cold, which contracts the capillaries,and falls in a warm tempera-ture, which leads to the dilata-tion of the capillaries, and thisshows too that local variationsin the contraction of the ves-sels influence the pressure ofthe blood in the rest of thesystem. Constriction of a par-ticular artery causes diminishedflow through the artery itself,increase of the pressure of theblood throughout the arterialsystem, and augmentation oftheflow of blood through all theother arteries of the body; whilstdilatation of an artery has theopposite effect. Fick,* from ex-periments made on the dog withhis modified spring manometer(Fig. 146), found the pressurein the right auricle nil ( = at-mospheric pressure); duringinspiration it sank to 10 mercury below zero. Inthe right ventricle the pres-. Fieks Spring Kymograph.—a, C-spring; b b, support; c, rodwhich communicates the movements of the spring to the lever d,and thus to the writing-needle a, the verticality of the move-sure varied from 18—42 mm., ment of which is secured by the second rod e; e, leaden tube byi • ,i if, , • i ,-I which the cavity of the spring is in communication with the maximum was 140 mm. The pressure of the blood in the aorta rose as high during the period of systoleas in the ventricle, but it did not fall so low during the diastole. Badoud,tworking under Fick and using his C-spring manometer, found the pressure ofthe blood in the pulmonary artery constantly below 60 mm. of mercury;after section of the spinal cord it fell considerably, and when the cord wasstimulated electrically it not only rose, as occurs in the systemic arteries, butrose considerably above the normal, this being due to the muscular contractionexcited in the body generally. Worm Mi
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectphysiology, bookyear1
