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Fig. 49-51 Human Embryos

The embryo to which we now come may be considered not only from the left side (Fig. 49) hut also from the dorsal (Fig. 50) and ventral (Fig. 51) surfaces.

It is the Hochstetter embryo Ma. 3, Fig. XXVII of the Keibel-Elze Normentafel and Figs. 7, 8, and 9 of Hochstetter's series. The trunk region has again begun to elongate. The spiral twisting is evident only to a slight extent in the tail region, the tail lying to the left of the belly stalk.

The nape bend is almost a right angle; the cerebral hemispheres are recognizable externally; and the cerebellum shows out plainly, especially in the ventral view (Fig. 51).

The axes of the upper limbs are almost parallel to the dorsal line; the hand plates are almost circular; the elbows show especially distinctly in the dorsal view (Fig. 50); and in the same view one may perceive, on the surface of the upper limb which looks towards the trunk, a small tubercle. In the lower limb the foot plates are marked off. Dorsal to the row of primitive somites one can clearly distinguish Schultze's segmentation of the sclerotomes. The maxillary processes have come into relation with the median nasal process, the openings of the nasal pits look towards the wall of the pericardium and are no longer to be seen from the side, especially from the left. A distinct sculpturing is present on the mandibular process and especially on the hyoid arch. The entrance into the sinus cervicalis is still visible as a small triangular hole.

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