All these,

then have a single stomach, and after that the gut;
but the stomach in some is comparatively large, as in the pig and
bear, and the stomach of the pig has a few smooth folds or ridges;
others have a much smaller stomach, not much bigger than the gut, as
the lion, the dog, and man. In the other animals the shape of the
stomach varies in the direction of one or other of those already
mentioned; that is, the stomach in some animals resembles that of
the pig; in others that of the dog, alike with the larger animals
and the smaller ones. In all these animals diversities occur in regard
to the size, the shape, the thickness or the thinness of the
stomach, and also in regard to the place where the oesophagus opens
into it.