316 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



pylorus. Between it and the pylorus is the " antrum pylori," of which the 

 distinguishing features are the comparative smoothness and paleness of the 

 mucous membrane, the presence of the pyloric as distinguished from the fundic 

 glands, and the existence of a relatively very strong musculature. 



The movements of the stomach during digestion have been the subject of 

 much study and experimentation, both in man and the lower animals, but it 

 cannot be said that the mechanism of the movements is as yet completely 

 understood. The fundamental facts to be borne in mind are that during a 

 period of several hours after ordinary food is received into the stomach the 

 musculature of this organ contracts in such a way as to keep the contents in 

 movement, while from time to time the thinner portions of the semi-digested 

 food are sent through the pylorus into the duodenum. There is a certain 

 orderliness in the movement, and especially in the separation and ejection of 

 the more liquid from the solid parts, which indicates that the whole act is 

 well co-ordinated to a definite end. The older physiologists spoke of a selec- 

 tive power of the pylorus in reference to the recurring acts of ejection of the 

 more liquid portions into the intestine, but a phrase of this kind, as applied to 

 a muscular apparatus, is permissible only as a figure of speech, and throws no 

 light whatever upon the nature of the process. It has been the object of 

 recent investigations to discover the mechanical factors involved in these acts 

 and their relations to the musculature known to be present. It has been shown 

 satisfactorily that the movements, of the stomach are not dependent upon its 

 connection with the central nervous system. The stomach receives a rich sup- 

 ply of extrinsic nerve-fibres, some of which are distributed to its muscles and 

 serve to regulate its movements, as will be described later ; but when these 

 extrinsic nerves are all severed, and indeed when the stomach is completely 

 removed from the body, its movements may still continue in apparently a 

 normal way so long as proper conditions of moisture and temperature are 

 maintained. We must believe, therefore, that the stomach is an automatic 

 organ, using the word automatic in a limited sense to imply essential independ- 

 ence of the central nervous system. The normal stomach at rest is usually 

 quiet, and the stimulus to its movements comes from the presence of the solid 

 or liquid material received into it from the oesophagus. Upon the reception 

 of this material the movements begin, at first feebly but gradually increasing in 

 extent, and continue until most or all of the material has been sent into the 

 duodenum, the length of time required depending upon the nature and amount 

 of the food. The exact character of the movements has been variously de- 

 scribed by different observers. Upon man they were carefully studied by 

 Beaumont 1 in his famous observations upon Alexis St. Martin (see p. 225), 

 and the essential points in his description have of late years been confirmed by 

 experiments upon dogs, 2 whose stomachs closely resemble that of man. These 



1 The Physiology of Digestion, 1883. 



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

 Moritz : Zeitschrift fur Biologie, 1895, Bd. xxxii. ; Eossbach : Deutsches Archiv fur klinische 

 Medicin, 1890, Bd. xlvi. 



