[Functional and morphological differentiation of the allantoic endoderm under the influence of the proventricular mesenchyme in the avian embryo].

The allantoic endoderm of Chick and Quail embryo associated with mesenchyme from 5 to 6-days proventriculus, differentiates into a proventriculus-type epithelium. The glands develop well and produce pepsin, an enzyme characteristic of the proventirculus. Splanchnopleure mesenchyme of the 3-day embryo is also able to bring about the heterotypic differentiation of allantoic endoderm.