THE DIFFERENTIATION OF RESPIRATORY CENTERS

Abstract

The localization of a dorsal expiratory center and a ventral inspiratory center (Pitts, Magoun and Ranson, Amer. Jour. Physiol. 126: 273, 1939) in the caudal part of the medulla oblongata was subjected to further exptl. test. The distance of current spread and the ability to localize a known structure was assessed by stimulation of the descending root of the trigeminal nerve through bipolar needle electrodes oriented in the Horsley-Clarke stereotaxic instrument while recording the antidromic impulses in the frontal division of the ophthalmic nerve. This method showed that currents of moderate intensity spread less than 0.5 mm. from the point of the electrodes and that a structure such as the descending trigeminal root could be localized within similar limits. Repeating the medullary exploration with the same technique, the original localization of dorsal expiratory and ventral inspiratory centers was confirmed.