128 IXSAL1VATION. 



find a bolus fixed and choking an animal, which from its size 

 might have readily passed downwards. 



The oesophagus is devoid of sensibility, and we do not feel 

 the passage of any ordinary bolus; but when injured, the 

 pain and irritation are intense, and death may speedily result. 

 This occurs in cases of ligature of the oesophagus, and many 

 of the facts observed by toxicologists, regarding the effects of 

 poisons which they caused the stomachs of dogs to retain by 

 ligature of the oesophagus, have proved quite unreliable from 

 the influence afterwards observed to attend the simple liga- 

 ture of the canal. 



The act of swallowing is not due to gravitation, as some 

 persons have supposed, and though liquids descend more 

 rapidly than solids, they call into play the vermicular con- 

 traction of the organs of deglutition. In vomiting and 

 rumination, we observe a regurgitation of food and liquids as 

 rapid as their passage downwards : and such regurgitation is, 

 as we shall afterwards show, due to an anti- vermicular con- 

 traction from the stomach to the mouth. 



