ELEMENTARY EXPERIMENTAL PHYSIOLOGY 



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food can be seen steadily ascending the oesophagus at about one-third 

 the rate it descends in the vertical 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 cardiac 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 



FIG. 194. Diagram of shadow of stomach. F = fundus ; Pc=pyloric canal ; U= umbilicus. 



represents the gas normally present in the fundus of the empty 

 stomach. More of the bread and milk 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. Consequently the upper 

 and lower limits of the shadow remain almost constant, whatever quantity 

 of food is present. When the whole of the meal has been taken, the 

 outline of the stomach should be marked on the screen, together with 

 the position of the umbilicus. In nearly every case the greater 



