Abstract
In a recent study by Dr. R. M. Pearce and myself of the mechanism of certain experimental conditions of low blood pressure, the following difficulties were encountered:
1. When substances that have been shown by special experiments to exert a selective peripheral action are injected into the circulation of an intact animal, the results frequently point to some additional central action that tends to mask or to neutralize to some extent the usual peripheral action.
2. Substances that have an essentially central action may sometimes produce results to be explained only on the basis of an added peripheral influence.
3. In experiments accompanied by a condition of extreme low blood pressure it is often difficult to know whether to ascribe these final results directly to the primary assault on the central or peripheral mechanism respectively, or to the additional secondary effects produced by the cerebral anemia that is the concomitant of the lowered systemic blood pressure. It is evident, therefore, that a knowledge of the extent and importance of the part played primarily by the central and peripheral mechanisms respectively, and by the central mechanism secondarily, in the production of any given result, is necessary for the interpretation of the mode of action of the substance used.
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