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
Catalogue details

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.

    34/462 (page 104)
    part of the respiratory tract is less sensitive than the larynx and nasal mucous membrane. In fact as we proceed downwards along the respiratory tract the mucous membrane is found to be less and less sensitive to chemical irritants. If, however, a small drop of chloroform be placed on the trachea it is at once followed by marked cardiac inhibition. By making use of more irritant vapours, e.g. a small amount of bromine, the reaction on heart and respiration can be produced in an intense form. In Fig. 5 we reproduce a curve showing how easily bromine vapour Fig. 5. Dog. Blood-pressure tracing. The zero-abscissa line has been raised 15 mm. Time tracings seconds. During the time indicated on the abscissa line the animal was made to breathe out of a bottle containing a small quantity of bromine vapour. The animal was breathing through a tracheal cannula, so that the upper parts of the respiratory tract are not affected during the experiment. produces the cardiac inhibition when it is inhaled directly into the bronchi and lungs. The effect is, as we should expect, still more marked if the vapour can act upon the nasal mucous membrane or upon the larynx. The result produced in this experiment is practically identical with that following electrical excitation of the central end of a pulmonary nerve—the only difference being a less sudden onset, which may well be due simply to the fact that the vapour takes a little time to gain free access to the mucous membrane. The reaction is much quicker in onset and far more intense than that following mechanical excitation of the alveolar nerves. That the reflex is, however, due to excitation of these pulmonary nerves is proved by Fig. 6, which was recorded at a later time from the same animal as in Fig. 5. Between the taking of these two records, however, the pulmonary