Collected papers (Part I.) from the Research Laboratories of the Royal College of Physicians, London, and the Royal College of Surgeons, England / edited by T.G. Brodie.

Date:
1903
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Licence: In copyright

Credit: Collected papers (Part I.) from the Research Laboratories of the Royal College of Physicians, London, and the Royal College of Surgeons, England / edited by T.G. Brodie. Source: Wellcome Collection.

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    affecting heart or vessels, nor to any alteration in the gaseous respiratory exchanges. He also proves that the acceleration during inspiration is due to an alteration of the tone of the cardio-inhibitory centre and that the afferent fibres which are excited are those of the lungs. Sommerbrodt* confirmed these results and moreover paid especial attention to the blood-pressure changes which accompanied them. He found that there was always a fall in blood-pressure, part of which was due to reflex dilatation of the blood vessels, and brings forward experiments to show that the rate of blood-flow through the capillaries is favoured by the fresh condition produced as a reply to the stimulation, which in itself tends to impede the flow. Leon Fredericq’* however questions the interpretation of these experiments. He considers that the effect is not reflex but is an automatic action of the cardiac centre and is quite independent of any reflex activity that can be induced from stimuli originating in the lungs. One of us® has described an effect produced by injecting serum into the circulation in a cat. This causes reflex arrest of the heart and of respiration and a diminution in tone of the vaso-motor centre. All these effects are cut out by section of the pulmonary nerves. Before we were familiar with the details of the work of these observers we had independently carried out many experiments upon the same lines. We can entirely confirm the results arrived at by Hering, When a fairly high pressure is used for the respired air the rate of heart-beat may fall to one-half its former pace, but there is never that very marked slowing which follows excitation of the central end of one of the pulmonary nerves. We have also shown that during the whole of the time that artificial respiration is being carried out upon an animal the heart is constantly inhibited as a result of the inflation. This is true both in curarised and non-curarised animals. It is more particularly marked in animals in which the thorax is open, and in which the total volume changes of the lungs are consequently exaggerated. With regard to the effect upon the vaso-motor centre we found, that suddenly changing the pressure of the respired air from atmospheric to a positive or negative pressure causes a fall in blood-pressure which is approximately proportional to the change in air pressure. This fall is also produced in atropinised animals and plethysmographic experiments * Sommerbrodt. Zeitschr. f. Idin. Med. ii.-g. ^01. 1881. - L^on Fredericq. Arch, de Biol. iii. p. 80. 1882. * Brodie. This Journal, xxvi. p. 48.