THE RESPIRATORY EFFECTS OF LOCALIZED FARADIC STIMULATION OF THE MEDULLA OBLONGATA

Abstract

The medulla oblongata of the dog was explored with fine stimulating electrodes; variations in respiration resulting from faradic stimulation were recorded. Small electrolytic lesions, approx. 0.5 mm. in diam., made possible histological control of the sites of stimulation as well as control of the size of the stimulation field. Responses to stimulation at 0.5 to 1.5 v. were usually abolished by the lesion. These responses consisted of 4 types of rate increases and 4 types of rate decreases with various amplitude changes. There was no segregation of similar responses in any uniform medullary field. Maximal inspiratory and expiratory re-sponses could be obtained upon stimulation with higher voltages, but these were not abolished even by lesions enormously larger than those sufficient to abolish the low-voltage responses. The differentiation of the inspiratory and expiratory centers described for the cat with the use of high voltages was not confirmed in the dog. The reticular formation of the medulla oblongata is probably the seat of the primary respiratory neurons and there is no differentiation of function within the formation demonstrable with the use of highly localized selective stimulation.