208 



PRACTICAL PHYSIOLOGY 



about midway along the greater curvature. As they pass slowly 

 towards the pylorus they become steadily deeper, until about one inch 

 from the entrance into the pyloric canal, the extreme pyloric end of 

 the stomach is, as a rule, completely separated from the rest of the 

 organ (Fig. 197). The part thus cut off gradually diminishes in size 

 owing to the further passage of the peristaltic wave and the simul- 

 taneous contraction of its longitudinal muscle-fibres. Its contents 

 can be seen to pass partly backwards as a reflux stream into the 

 stomach and partly through the narrow pyloric canal into the 

 duodenum. 



m 



FIG. 197. Peristalsis in the stomach. 



Intestines. The shadow of the duodenum cannot, as a rule, be very 

 definitely seen, owing to the rapid passage of the bismuth out of it 

 and the diminished concentration of the salt due to the large quantities 

 of digestive secretions mixed with it. The motor activity of the 

 small intestine can therefore only be satisfactorily studied some hours 

 later. 



A second examination should be made between four and five hours 

 after the bismuth meal. The stomach is then generally empty. The 

 shadow of the caecum is seen in the right iliac fossa, and in some 

 individuals a small part of the ascending colon is also visible; the 

 appendix can only be recognised on rare occasions. This examination 

 shows that about four hours are required for the passage of food 



