ADVANCED EXPERIMENTAL PHYSIOLOGY 



act and the disappearance of the last trace of fluid from the 

 oesophagus should be measured with a stop-watch. It varies 

 between four and nine seconds in different individuals. About 

 one-half of the total period is required for the food to reach the 

 lower end of the oesophagus, the other half being required for its 

 passage through the cardia. 



Fig. 165 represents diagrammatically the shadow as seen at 

 intervals of a second. 



In the horizontal position the fluid passes along the oesophagus 

 slightly less rapidly than in the vertical position. A similar but 

 more prolonged delay takes place while the food passes through the 

 cardia, the prominent 

 end of the column 

 being in this case 

 rounded. Sometimes 

 a small quantity of 

 the food follows more 

 slowly, and appears 

 as a thin streak in- 

 stead of the com- 

 paratively broad 

 band seen when the 

 oesophagus is filled. 



In the inverted 

 position, with the 

 head directed down- 

 wards, the food can 

 be seen steadily as- 

 cending the oesopha- 

 gus at about one- 

 third the rate it 

 descends in the ver- 

 tical position. Owing 

 to its slower passage, 

 the final delay at the 

 cardia is less obvious. 



Sometimes a little fluid runs back from the stomach into the car- 

 diac end of the oesophagus, whence it once again passes into the 

 stomach. 



The Stomach.- The X-ray tube is now lowered so that the rays 

 may traverse the abdomen, and the individual faces directly 

 forwards. Under the left half of the diaphragm a transparent area 

 is visible, which represents the gas normally present in the fundus 

 of the empty stomach. More of the meal is now swallowed, and it 

 can be seen entering the fundus to the right of this clear area ; the 

 shadow of the stomach becomes gradually more obvious as more of 

 the food is taken. The tone of the stomach diminishes as more food 

 enters, so that the intragastric pressure remains constant. Conse- 

 quently the upper and lower limits of the shadow remain almost 



H 



FIG. 166. Diagram of shadow of normal 



stomach. 

 F = fundus ; P.c = pyloric canal ; U = umbilicus. 



