THE MOVEMENTS OF THE STOMACH 783 



to the nature of the food taken, the arrival of one of these waves of 

 contraction at the pylorus causes a relaxation of the orifice, and 

 a few cubic centimetres of gastric contents are squirted into the 

 first part of the duodenum. While these movements of the pyloric 

 mill are going on, the cardiac portion of the stomach is exercising a 

 steady pressure on its contents in consequence of a tonic contraction 

 of its muscular wall, so that each successive portion of the food 

 mass which is loosened by the digestive action of the gastric juice 

 is forced on into the pyloric mill. As digestion proceeds the opening 

 of the pylorus becomes more frequent. The stomach empties itself 

 more and more, until finally the whole of the viscus has the shape 

 of a curved tube (Fig. 335). At the very end of digestion the pylorus 

 may open to allow the passage even of undigested morsels of food. 



Very similar .are the changes in the human stomach, as shown by 

 Hertz. The term fundus is by him limited to that part of the 

 stomach situated above the cardiac orifice (in the erect position). 

 The body of the stomach is marked off, more or less, by the incisura 

 angularis on the lesser curvature corresponding to what we have 

 called the transverse band. The pyloric portion consists of the 

 pyloric vestibule and the pyloric canal, the latter being a tubular 

 portion about 3-0 cm. in length, especially well marked in infants. 

 When a small quantity of food has been swallowed (in the erect 

 position) its weight is sufficient to overcome the resistance of the 

 contracted gastric wall, and it rapidly passes to the pyloric part. 

 Peristalsis begins almost at once, each constriction starting near 

 the middle of the stomach, and deepening as it slowly progresses 

 towards the pylorus (Fig. 336). About one inch from the pyloric canal 

 it is so marked that part of the pyloric vestibule becomes almost com- 

 pletely separated from the rest of the stomach. The part thus cut 

 off then diminishes in size in every direction, part of its contents 

 being forced through the pyloric canal, while the remainder escapes 

 back as an axial reflux stream into the stomach. The waves recur at 

 regular intervals of fifteen to twenty seconds, and three or four are 

 present simultaneously. They continue without cessation until the 

 stomach is empty from one to four hours after the meal according 

 to its bulk and composition. 



The foregoing descriptions apply especially to the events which 

 succeed the taking of a considerable meal. If warm fluid alone, 

 e.g. water, be swallowed, the opening of the pylorus occurs within 

 a very short time after the fluid has reached the stomach. Thus if 

 a large draught of water be taken to quench thirst it may arrive 

 in the duodenum within a minute or two after being swallowed, and 

 it is from the duodenum and small intestine that any absorption 

 place, When a meal is undergoing Digestion, there* is a 



