NERVOUS CONTROL OF RESPIRATION

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Abstract
An operative method is described by which the floor of the 4th ventricle can be exposed without interfering with the respiratory or vasomotor mechanisms, reflex polypnea occurring spontaneously or being induced experimentally. The light anesthesia polypnea mechanism is very sensitive to surgical manipulation, can be entirely eliminated without affecting the ordinary mechanism of quiet respiration and the region about or just caudal to the inferior colliculi is especially sensitive. Polypnea is not dependent on centers situated in the reticular formation, or on fiber tracts crossing the mid-line or passing cephalad or caudal through the medial stems of the isthmus, pons, or upper medulla. If polypnea is dependent on cephalic centers, the centers as well as the fiber tracts passing to and from the centers are located in the extreme lateral stems of the pons and upper medulla. Although lesions that cut the lateral stems eliminate polypnea, this does not necessarily mean that anatomical structures concerned with respiration are destroyed. It is demonstrated that the typical respiratory acceleration response that can be obtained through a sciatic during light anesthesia can still be obtained with the brain-stem hemi-sectioned through the upper medulla level. Section of the opposite side of the stem eliminated the response. Short rapid respiratory excursions superimposed upon the inspiratory phase of the slower ordinary respiratory excursions as a result of unilateral lesions were elicited re-flexly through a sciatic stump or by means of a heat beam. Ordinary quiet respiration was slowed by sectioning only 1 lateral stem through the pons region just as by sectioning the whole brain-stem at this level. Sectioning the opposite lateral stem after the 1st has been sectioned caused a further slowing of. the respiratory rate. An animal can respire in a normal and coordinated manner with vagi cut and with 1 lateral stem sectioned through the caudal region of the pons. In the cases observed section of the opposite lateral stem at this level eliminated coordinated respiratory movements.

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