Abstract
It is desirable and even necessary, in attempting to estimate the rôle of the afferent nerves in the regulation of the respiratory movements 1 to investigate more carefully the effects upon respiratory movements of changes in the volume of blood flowing through the medulla oblongata. 2
The experiments described here were done on cats. Etherization and tracheotomy were routine procedures. Some of the cats were decerebrated, after which no more ether was necessary. The two common carotid and two vertebral arteries were isolated in the neck so that they might be ligated temporarily or permanently. Blood pressure was taken from the left carotid artery and the respiratory movements recorded by a Crile stethograph and a Verdin tambour. Blood for the estimation of the carbon dioxide was drawn from the femoral artery, and the estimations were made by the Van Slyke method. Changes in the volume of blood flowing through the medulla were brought about by occluding the cerebral arteries. Control samples of blood were taken at the beginning of each experiment. Other samples were taken during the period of occlusion of the cerebral arteries and after the release of these arteries and the restoration of the cerebral circulation. In some of the experiments, the arteries were never occluded, but changes in the blood flow to the medulla were produced by successive small hemorrhages of eight to ten cubic centimeters each. Pulse counts in some of these experiments were made by Miss Ethel Wickwire.
Simple occlusion of the cerebral arteries was sufficient to produce severe dyspnoea in some animals, but in others, dyspnoea appeared only after a considerable quantity of blood had been drawn. In all animals, the effects of the occlusion became more and more severe as more and more samples of blood were drawn.
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