This and the De ovo incubato (No. 468) placed the study of embryology on a sound basis, surpassing in accuracy all other contemporary work on the subject and foreshadowing some of the more important general lines of research in embryology. Malpighi's study of the development of the chicken in the egg went far beyond the work of Harvey and Fabrici, dealing with the internal structures to an unprecedented extent: his chief discoveries, illustrated in his four beautifully detailed plates, were the vascular area embraced by the terminal sinus, the cardiac tube and its segmentation, the aortic arches, the somites, the neural folds and neural tube, the cerebral and optic vesicles, the protoliver, the glands of the prestomach, and the feather follicles. According to Adelmann, Malpighi illustrated very clearly the three primary brain vesicles, and then the five secondary brain vesicles (along with the two optic vesicles).English translation in No. 534.1.