SUPERIOR XARYNGEAL SERVES. 219 



when they are touched with a piece of meat, regular and 

 natural movements of deglutition ensue. In the recent and 

 elaborate experiments of Waller and Prevost, it was shown 

 that, after division of the superior laryngeals, excitation of 

 the parts supplied with sensory filaments by these nerves 

 produced no movements of the pharynx. 1 



The experiments made by galvanizing the trunks of the 

 nerves are extremely interesting. If the nerves be divided 

 and galvanization be applied to their central ends, move- 

 ments of deglutition are observed, and there is also arrest 

 of the action of the diaphragm. From these experiments, 

 first elaborated by Rosenthal, 3 it would seem that the im- 

 pression which gives rise to the movements of deglutition 

 aids in protecting the air-passages from the entrance of for- 

 eign matters, by temporarily arresting the inspiratory act. 

 These experiments of Rosenthal have been repeated very 

 extensively by physiologists ; and concerning the effects of 

 galvanization of the superior laryngeals upon respiration, 

 there is considerable difference of opinion. 



The important point for our consideration, in this con- 

 nection, is the action of the nerves in the ordinary phe- 

 nomena of deglutition ; and in experiments with galvanism, 

 a feeble current simulates most nearly the natural pro- 

 cesses. In such experiments, the results have been quite 

 satisfactory. Waller and Prevost used a very feeble current, 

 and confirmed entirely the observations of Hosenthal. They 

 found, also, that galvanization of the roots of the pneumo- 

 gastrics above the origin of the laryngeals produced the same 

 effects as galvanization of the trunks of the superior laryn- 

 geals. 3 The experiments in which a powerful current of 



1 WALLER ET PREYOST, op. cit. Archives de physiologic, Paris, 1870, tome 

 iii., p. 347, el seq. 



9 ROSESTHAL, De ^influence du nerf pneumogastrique el du nerf larynge supe- 

 rieur sur Ics mouvements du diaphragm. Comptes rendus, Paris, 1861, tome Hi., 

 p. 754 ; and, Die Athembewegungen und ihre Beziehungen zum Nerous vagu?, Ber- 

 lin, 1862, S. 72. 



8 Loc. cit. 



