MOVEMENTS OF THE ALIMENTARY CANAL, ETC. 315 



sensory fibres to this area arise from the trigeminal nerve. The same observer, 

 in experiments upon himself, was unable to locate any particular area of the 

 mucous membrane of the mouth which seemed to be especially connected with 

 the swallowing reflex. The physiological centre of the reflex is supposed to lie 

 quite far forward in the medulla, but its anatomical boundaries have not been 

 satisfactorily defined. It seems probable that in this as in other cases the 

 physiological centre is not a circumscribed collection of nerve-cells, but com- 

 prises certain portions, more or less scattered, of the nuclei of origin of the 

 efferent fibres to the muscles of deglutition. These muscles are innervated by 

 fibres from the hypoglossal, facial, trigeminal, glossopharyngeal, and vagus. 

 The latter nerve supplies through some of its branches the entire oesophagus 

 as well as some of the pharyngeal muscles, the muscles closing the glottis, and 

 the aryteno-epiglottidean, which is supposed to aid in depressing the epiglottis. 



MOVEMENTS OP THE STOMACH. 



The musculature of the stomach is usually divided into three layers, a lon- 

 gitudinal, an oblique, and a circular coat. The longitudinal coat is continuous 

 at the cardia with the longitudinal fibres of the oesophagus ; it spreads out from 

 this point along the length of the stomach, forming a layer of varying thick- 

 ness ; along the curvatures the layer is stronger than on the front and posterior 

 surfaces, while at the pyloric end it increases considerably in thickness, and 

 passes over the pylorus to be continued directly into the longitudinal coat of 

 the duodenum. The layer of oblique fibres is quite incomplete ; it seems to be 

 continuous with the circular fibres of the oesophagus and spreads out from the 

 cardia for a certain distance over the front and posterior surfaces of the fuudus 

 of the stomach, but toward the pyloric end disappears, seeming to pass into 

 the circular fibres. The circular coat, which is placed between the two pre- 

 ceding layers, is the thickest and most important part of the musculature of 

 the stomach. At the extreme left end of the fundus the circular bands are 

 thin and somewhat loosely placed, but toward the pyloric end they increase 

 much in thickness, forming a strong muscular mass, which, as we shall see, 

 plays the most important part in the movements of the stomach. At the pylo- 

 rus itself a special development of this layer functions as a sphincter pylori, 

 which with the aid of a circular fold of the mucous membrane makes it 

 possible to shut off the duodenum completely or partially from the cavity 

 of the stomach. The portion of the stomach near the pylorus is fre- 

 quently designated simply as the " pyloric part," but owing to its distinct 

 structure and functions the more specific name of "antrum pylori" seems 

 preferable. The line of separation between the antrum pylori and the body 

 or fundus of the stomach is made by a special thickening of the circular fibres 

 which forms a structure known as the " transverse band " by the older 

 writers, 1 and described more recently 2 as the "sphincter antri pylorici." 

 This so-called sphincter lies at a distance of seven to ten centimeters from the 



1 See Beaumont: Physiology of Digestion, 2d ed., 1847, p. 104. 



2 Hofmeister und Schiitz : Archiv fur exper. Pathologic und Pharmakoloffie, 1886, Bd. xx. 



