CHAPTER X. 



THE POSTERIOR PITUITARY AS THE FUNCTIONAL 

 CENTER OF THE NERVOUS SYSTEM, AND 

 AS THE ANTERIOR PITUITARY'S CO- 

 CENTER IN SUSTAINING THE 

 VITAL PROCESSES. 



THE IDENTITY OF THE LOWER BRAIN, OR CENTRAL 

 NERVOUS SYSTEM. 



IN the ninth chapter we ventured to suggest that none of 

 the medullary nervous centers could be considered as "inhib- 

 itory" or "respiratory" in the physiological sense now accorded 

 these terms, and we stated that the phenomena ascribed to 

 these centers were regarded by us as (1) the result of excessive 

 (and therefore pathological) stimulation of the vagus as re- 

 gards cardiac inhibition, and (2) of the interruption of general 

 motor impulses which the medulla serves to transmit, in re- 

 spect to the respiratory phenomena. Paradoxical as the state- 

 ment may seem, our views are confirmed by the investigations 

 of the brothers Weber (1845), who first suggested that the 

 heart could be "inhibited" by stimulation of a corresponding 

 medullary center. Their experiments differed from those we 

 have reviewed in that the cerebro-spinal structures themselves 

 were submitted to the effects of the current, thus concentrat- 

 ing the latter upon the areas in which the "inhibitory" centers 

 were supposed to exist. One pole having been placed in the 

 nasal cavity of a frog and the other on the spinal cord over 

 the fourth or fifth vertebra, the heart's action momentarily 

 ceased, then gradually resumed its normal activity. Approxi- 

 mation of the poles upon the cerebral hemispheres and stimu- 

 lation of the cord produced no effect upon the heart. "Not 

 until the medulla oblongata between the corpora quadrigemina 

 and the lower end of the calamus scriptorius was stimulated," 

 says Professor Porter, "did the arrest take place. Cutting 

 away the spinal cord and the remainder of the brain did not 

 alter the result." Our views are likewise sustained by the 

 effects of experimental injury of the medullary area which 

 Flourens termed le nceud vital, or "ganglion of life." 



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