68 



In my treatise on tlie Structure and Animal 

 GEconomy of the Horse, I gave my reasons for 

 doubting the fact of the wind being sucked 

 into the stomach during^ the action of crib- 

 biting ; and, on a careful revision of the doc- 

 trine I held upon that subject, I have found no 

 cause to alter my opinion. That an accumu- 

 lation of air takes place in the stomach and 

 intestines of horses of that description, is not 

 to be denied ; but I believe that the air is col- 

 lected from other causes, and is not sucked in 

 at the mouth of the animal. In order, tho- 

 roughly, to comprehend the basis of this opini- 

 on, it is necessary to consider the anatomical 

 form of the organs of respiration. The whole 

 space of the atmosphere being filled with air, 

 which constantly maintains its equilibrium, none 

 of that air can be sucked in until a cavity is 

 formed for its reception : thus, no air can be 

 sucked into the mouth, unless the chest opens 

 and expands itself to receive it ; that is to say, 

 no air can be drawn inwards except at that 

 period of the act of breathing distinguished by 

 the term " inspiration." Now the mouth of 

 the trachea or windpipe is always open for the 

 ingress and egress of air, except at the moment 

 when food or liquids are swallowed, and pass 

 over it into the oesophagus or passage into the 

 stomach. Tlicrefore, supposing the animal 

 swallowed the air coutaincd in his mouth by 



