The fall of blood pressure resulting from the stimulation of afferent nerves / by Reid Hunt.

  • Hunt, Reid, 1870-1948.
Date:
1895
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Credit: The fall of blood pressure resulting from the stimulation of afferent nerves / by Reid Hunt. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    pressure still rose, on stimulation of sensory nerves, after the complete removal of the hemispheres. The first and apparently only thorough investigation of the afferent nerves concerned in this reflex was made by Latschenberger and Deahna1. From a study of the forms of the curves of blood-pressure during stimulation of various afferent nerves, from the fall of pressure obtained by long-continued stimulation of the sciatic, and especially from the fall following the removal of a clamp from the femoral artery, they concluded that from all the blood vessels of the body depressor as well as pressor nerve-fibres run to the vaso-motor centre. They thought further, that when the pressure in one vascular area was decreased (e.g. by clamping the artery) the pressor fibres were stimulated and a rise occurred, whereas, when the pressure is suddenly increased (as when the clamp was removed), the depressor fibres were stimulated and a fall of arterial pressure resulted. However, it was soon shown by Zuntz2 that it was the anaemia of the tissues rather than the pressure in the blood vessels which caused the reflex rise of pressure. Then the failure of several experimenters to find another nerve like the depressor, stimula- tion of which invariably caused a fall of pressure, lead some physiologists to the view that there are no depressor fibres in the sense used by Latschenberger and Deahna3, but that the fall of pressure sometimes obtained is due to the condition of the centre4. It is true that writers sometimes speak of depressor fibres in the sciatic and other nerves, and Bayliss5 has recently put forward a theory of their action, but the possibility that the fall of pressure in these cases is due to changes in the centre was not excluded6. Howell7 has recently published an account of experiments made by himself and some of his pupils, on the effects of cold upon the con- 1 Latschenberger and Deahna. Pfliiger's Archiv, xn. 157. 1876. 2 Zuntz. Pfliiger's Archiv, xvn. 404. 1878. 3 Tigerstedt. Op. cit. p. 525. 4 See Knoll. Sitzber. d. Akad. d. Wiss. z. Wien, Math.-naturw. 01., 92, Abth. 3, p. 451. 1885. Also Foster, Text-book of Physiology, 6th ed. p. 345. 1893. 5 Bayliss. This Journal, xiv. 317. 1893. 6 After this paper had been written my attention was called to a section in the article by Bradford and Dean on the Pulmonary Circulation (This Journal, xvi. 67. 1894), in which they describe the effect of stimulation of the central ends of the intercostal nerves. They state that stimulation of the central ends of certain of these nerves is followed by a fall of pressure while that of the sciatic is followed by a rise, and argue from this that, as the vaso-motor centre is in normal condition, the fall can probably be explained only by supposing that there are two sets of fibres here—pressor and depressor. 7 Ho well, Budgett and Leonard. This Journal, xvi. 298. 1894.