File:Kirkes' handbook of physiology (1907) (14583158639).jpg

Identifier: kirkeshandbookof00kirk (find matches)
Title: Kirkes' handbook of physiology
Year: 1907 (1900s)
Authors: Kirkes, William Senhouse, 1823-1864 Greene, Charles Wilson, 1866-1947
Subjects: Physiology
Publisher: New York, W. Wood and company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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ly for hours on purely inorganic INFLUENCE OF THE CENTRAL NERVOUS SYSTEM 179 nutrient fluid, provided only that the oxygen be supplied in sufficientquantity and under high enough tension. THE REGULATIVE INFLUENCE OF THE CENTRAL NERVOUSSYSTEM ON THE HEART. The heart is capable of automatic rhythmic movement, yet while in thebody its beats are under the constant control of the central nervous system.The influence which is exerted by the central nervous system is of two kinds:first, in the direction of slowing or inhibiting the beats, and, second, in thedirection of accelerating or augmenting the beats. The influence of thefirst kind is brought to bear upon the heart through the fibers of the pneumo-gastric or vagus nerves, and that of the second kind through the sympatheticnerves. The Inhibitory Nerves. It has long been known, indeed eversince the experiments of the Weber brothers in 1845, that stimulation of oneor both vagi produces slowing of the rhythm of the heart. It has since been
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Fig. 177.—Effect on the Heart Rate and on the Arterial Blood Pressure of Stimulating theRight Vagus of the Dog. Stimulus applied at the mark on and removed at off. Pressure inmillimeters of mercury shown by the scale to the left. Time in seconds. (New figure by Hill andChilton.) shown, in all of the higher vertebrate animals experimented with, that thisis the normal reaction to vagus stimulation. Moreover, a section of onevagus, or at any rate of both vagi, produces acceleration of the pulse; andstimulation of the distal or peripheral end of the divided nerve normallyproduces slowing or stopping of the hearts beats. 180 THE CIRCULATION OF THE BLOOD It appears that any kind of stimulus, either chemical, mechanical, elec-trical, or thermal, produces the same effect, but that of these the most potentis a rapidly interrupted induction current. A certain amount of confusionhas arisen as to the effects of vagus stimulation in consequence of the factthat fibers of the sympathetic nerve run

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