File:A manual of human physiology, including histology and microscopical anatomy, with special reference to the requirements of practical medicine (1885) (14781433165).jpg

Identifier: manualofhumanphy01land (find matches)
Title: A manual of human physiology, including histology and microscopical anatomy, with special reference to the requirements of practical medicine
Year: 1885 (1880s)
Authors: Landois, L. (Leonard), 1837-1902 Stirling, William, 1851-1932
Subjects: Physiology Histology
Publisher: Philadelphia, P. Blakiston, Son, and Company
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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her hand, it is diminished owing to the diminu-tion of the air in the lungs acting upon the aorta. Besides, theinspiratory movements of the chest aspirate blood from the venaecavse towards the heart, while expiration retards it, and thus influencesthe blood-pressure. The undulations are most marked in the arterieslying nearest to the heart. The respiratory undulations are due in partto a stimulation or condition of excitement of the vaso-motor centre,Avhich runs parallel with the respiratory movements. This stimulationof the vaso-motor centre causes the arteries to contract, and thus theblood-pressure is raised. The variations in the pressure which dependupon a varying activity of the vaso-motor centre are known as thecurves of Traube and Hering (p. 171). In Fig. 77 are represented ablood-pressure tracing and a curve of the movements of respiration(thick line) taken simultaneously in a dog by C. Ludwig and Einbrodt.The blood-pressure tracing was obtained from the carotid artery, while
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Fig. 77. Kyinographic blood-pressure tracing (upper, thin line), and respiration curve(lower, thick line), taken simultaneously—ex, expiration ; in, inspiration ; c, c,heart-beats. The large curves in the blood-pressure tracing are due torespiration (Ludwig and Einbrodt). the pressure within the thorax was measured by means of a manometerplaced in connection with one pleural cavity. In this curve, whenexpiration begins (at ex), and as the expiratory-pressure rises, the blood-pressure rises, while when inspiration begins (at in) both fall. Theblood-curve, however, begins to rise (at c) before expiration com- 170 RESPIRATORY UNDULATIONS IN THE BLOOD-PRESSURE CURVE. mences—i.e., during the last part of the act of inspiration. Thisis due to the contraction of the arteries, caused by impulses sentfrom the vaso-motor centre. It is also aided by the circum-stance that during inspiration there is an increased inflow ofvenous blood to the heart, so that when it contracts, more blood isforc

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