X. On the gizzards of grazing birds

In the course of my enquiries into the various modes in which the food in different animals is prepared for digestion, many circumstances have been met with, which tend to shew, that grass is the substance of all others, on which animals feed, that requires the most preparation ; and that ruminating animals are fitted by nature in an eminent degree, for extract­ing the greatest possible quantity of nourishment from this species of food. If we examine the means employed by quadrupeds of this description, it will appear, that the grass in the first instance is broken short off from the ground and swallowed ; then macerated with the mass that had previously undergone some preparation in the first stomach, and afterwards a part of the whole of this mixture, before it is digested, is brought back into the mouth, there masticated in a particular manner; not as in the elephant and horse, or those nearest allied to them, but by being obliquely cut into smaller portions and then mixed up with the saliva into pellets, which are conveyed through the third stomach into the fourth, for the purpose of digestion. This is a mode of preparation peculiar to ruminants, no other quadruped being provided with all the same means.