Localization of the Medullary Respiratory Centers in the Cat1

Beginning with the work of Longet (1847) there has accumulated an impressive mass of evidence which indicates that the indispensable mechanism for the neural control of respiration is localized in the reticular formation of the caudal half of the medulla (Brown-Sequard, 1860; Gad and Marinesco, 1893; Bechterew, 1885; Kohnstamm, 1900; etc.). Although there have appeared sporadic assertions that isolated structures play a predominant role in respiratory control, e.g., the ala cinerea (Schiff, 1870; 1871), the tractus solitarius (Gierke, 1873), the central nuclei of the medullary raphe (Mislawsky, 1885), recent reviews of the subject by Finley (1931) and Cordier and Heymans (1935) adequately demonstrate the preponderant importance of the medullary reticular formation. A functional subdivision of the respiratory center into inspiratory and expiratory portions has been attempted by Marckwald and Kronecker (1880), Lewandowsky (1896), Mislawsky (1885) and Gad and Marinesco (1893). Lumsden (1923) claims to have distinguished 4 centers, a pneumotaxic, an apneustic, an expiratory and a gasping center. Henderson and Sweet (1929) maintain that only 1 respiratory center exists. Attempts at more definite localization within the reticular formation by the transection, partial section, isolated destruction and crude stimulation methods of the early investigators have succeeded only in delimiting the cephalic limits of the respiratory center as somewhere caudal to the entrance of the eighth nerves. Gesell, Bricker and Magee (1936) in a study of amplified potentials showing a respiratory rhythm tapped from the brain stem place the cephalic limit of the respiratory center within the reticular formation at the level of entrance of the upper vagal rootlets and the cephalic end of the inferior olive. The caudal limit they place 2 mm. below the obex at the level of the decussation of the pyramids. In view of the indefinite localization of the medullary respiratory center and the disagreement as to its functional subdivision it seemed to us that a careful study of the respiratory responses to stimulation of the brain stem