PREPARATION OF TISSUE-FUEL 



185 



turn to an examination of the construction of the stomach 

 — a preparatory factory for the production of tissue-fuel. 

 In fig. 40 the stomach has been laid open to show its 

 great chamber and its two doorways. The upper or 



OESOPHAGUS 

 SPHINCTER 



CARDIAC ORIFICE 



BOLUS 



FROM LIVER 



JEJUNUM 



DUODENUM 



Fig. 40. — The stomach laid open to show the cardiac and pyloric gateways. 



cardiac doorway, where the oesophagus opens, we have 

 already seen to be guarded by a short sleeve of muscle — 

 a sphincter mechanism. The lower or pyloric doorway 

 leading into the duodenum (fig. 40) is guarded by the 

 strongest sphincter in all the body, one always in action, 

 only relaxing sufficiently to let the more fluid part pro- 



