The influence of intravenous injections of magnesium sulphate upon the activities of the center of deglutition

Abstract

In order to understand our experimental results the following physiological facts have to be recalled. Three different phenomena which are under the reflex control of the center of deglutition must be distinguished: (1) The transmission of food from the mouth through the pharynx into the esophagus. This is a complex process which comprises the execution, in a coördinate and stable manner, of three separate activities: the closure of the entrances into the post-nasal cavity and into the larynx, and the rapid transportation of the contents of the mouth into the proper direction. We shall designate the entire action as the initial act of deglutition. The reflex mechanism which controls it, is more resistant to anesthesia than the two reflex mechanisms of the phenomena to be mentioned next. (2) The peristaltic movements of the esophagus. This is dependent only upon the occurrence of the first mentioned mechanism, the initial act of the deglutition, and is independent of the actual passing of some contents through the esophagus or of the anatomical continuity of the latter. Transection of the esophagus or complete removal of a 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 deglutition, 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 esophagus. 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.