| During its life cycle, Y. pestis colonizes the flea midgut and can form a biofilm in the proventricular valve in the foregut. |
| The commencing heart, formed at this stage of two distinct tubes, is attached to the ventral side of the foregut. |
| These grow inward and eventually fuse to form the endoderm of the midgut, while ectoderm is dragged inward behind them at each end to form the foregut and the hindgut. |
| Hence when the stomach develops from the foregut, as a specialized segment of the same, it is supplied by vagus branches. |
| Then, to turn that foregut into stomach tissue, they worked out you need to add a dash of retinoic acid. |
| That price is the very absence of the selenodont specializations, the most obvious of which is foregut fermentation. |
