Activities of Center of Deglutition. 107 



great part of it does not prevent the contraction in the lower part 

 of the esophagus or of the cardia in due time after the initial de- 

 glutition, a time which varies with different species of animals 

 (Mosso, Kronecker and Meltzer). The initial sensory impulse, 

 after reaching the center of deglutition, passes consecutively 

 through a number of sections of that center, sending, while thus 

 passing, motor impulses to the corresponding sections of the esoph- 

 agus. This reflex mechanism of primary peristalsis (Meltzer) is 

 very resistant to fatigue, but is less resistant to anesthesia than 

 any other of the reflexes with which we are here concerned. 

 (3) Local reflexes of secondary peristalsis (Meltzer). A mechanical 

 stimulus applied to any part of the mucosa of the esophagus (dis- 

 tension) will cause a contraction of the corresponding part of that 

 canal, and, if this stimulus is brought about by some movable 

 mass within the lumen of the esophagus, this mass will be driven 

 down into the stomach by a wave which is difficult to distinguish 

 from a wave of primary peristalsis. If the mass is mechanically 

 prevented from being moved downward, no contraction takes 

 place at any other part of the esophagus below the stimulating 

 mass. That the secondary peristalsis is due to a central reflex and 

 not to a peripheral mechanism, is proven by the fact that it disap- 

 pears as soon as the vagi are cut. This central reflex is readily 

 fatigued, but is, on the other hand, more resistant to central 

 anesthesia than the transmission of the impulse from section to 

 section within the center. 



For several years we were engaged, at various times, in bringing 

 forward evidences for the central nature of the inhibitory action 

 of magnesium salts. With this object in mind, we studied in the 

 present series of experiments the action of these salts upon the 

 primary and the secondary peristalsis of the esophagus. The 

 animals, dogs, received for anesthesia, three milligrams of morphin 

 per kilo body weight. This permitted the operative procedures 

 needed for our experiments, which consisted in exposing the trachea 

 and making a window in it below the larynx; the transection of 

 the esophagus and tying a glass tube in the upper end of it, the 

 exposing of one superior laryngeal nerve and of tying a cannula 

 in the external jugular vein. A short time after the operation the 

 initial act of deglutition could be brought on by either of the three 



