296 DIGESTION. 



food gradually propelled through the pylorus, but a kind 

 of double current is continually kept up among the con- 

 tents of the stomach, the circumferential parts of the mass 

 being gradually moved onward towards the pylorus by 

 the peristaltic contraction of the muscular fibres, while the 

 central portions are propelled in the opposite direction, 

 namely, towards the cardiac orifice ; in this way is kept up 

 a constant circulation of the contents of the viscus, highly 

 conducive to their free mixture with the gas.tric fluid and 

 to their ready digestion. 



These actions of the stomach are peculiar to it and inde- 

 pendent. But it is, also, -adapted to act in concert with 

 the abdominal muscles, in certain circumstances which can 

 hardly be called abnormal, as in vomiting and eructation. 

 It has indeed been frequently stated that the stomach 

 itself is quite passive during vomiting, and that the ex- 

 pulsion of its contents is effected solely by the pressure 

 exerted upon it when the capacity of the abdomen is 

 diminished by the contraction of the diaphragm, and sub- 

 sequently of the abdominal muscles. The experiments 

 and observations, however, which are supposed to confirm 

 this statement, only show that the contraction of the abdo- 

 minal muscles alone is sufficient to expel matters from an 

 unresisting bag through the oesophagus ; and that, under 

 very abnormal circumstances, the stomach, by itself, cannot 

 or rather does not expel its contents. They by no means 

 show that in ordinary vomiting the stomach is passive ; 

 and, on the other hand, there are good reasons for believing 

 the contrary. 



It is true that facts are wanting to demonstrate with 

 certainty this action of the stomach in vomiting ; but some 

 of the cases of fistulous opening into the organ appear 

 to support the belief that it does take place;* and the 



* A collection of cases of fistulous communication with the stomach, 

 through the abdominal parieties, has been given by Dr. Murchison in 

 vol. xli. of the Medico- Chirurgical Transactions. 



