food going through the human digestive system ( generally )only moves in ons direction . however ,in some animals, the food goes in two direction and come out of the same opening. in which animals does this happen? why ? why would this not work for in human.

Dear student ,
These animals quickly swallow the grass and store
it in a part of the stomach called
rumen.Here the food gets partially digested and is called cud.
But later the cud returns to the mouth
in small lumps and the animal chews
it. This process is called rumination and
these animals are called ruminants.
The grass is rich in cellulose, a type
of carbohydrate. In ruminants like cattle,
deer, etc.