Paper - A comparison of the Herzog and Strahl-Beneke embryos

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Lewis FT. A comparison of the Herzog and Strahl-Beneke embryos. (1917) Anat. Rec, 11: 386.

Online Editor  
Mark Hill.jpg This 1917 paper presented by Lewis at the 33rd Meeting of the American Association of Anatomists in New York (Dec 27-29, 1916). Describes two early human embryos (Carnegie stage 6) that had been previously serially sectioned.

The Strahl-Beneke embryo (Carnegie stage 6) was described originally by Strahl and Beneke in 1916 in a monograph and later by Florian and Beneke (1931). Chorionic cavity, 3.8 x 2.2 x 1.2 mm. Embryonic disc (narrow type), 0.375 mm (Florian, 1934a). Primitive streak (doubted by Rossenbeck, 1923, and denied by Fahrenholz, 1927, but acknowledged by Florian, 1928a), 0.1 mm. No notochordal process (Hill and Florian, 1931b). Prechordal plate, 0.066 mm. Dorsal and median projections published (Florian and Beneke, 1931, figs. 2 and 1; Florian, 1928a, fig. 42; Florian, 1945, plate 4, fig. 41; Mazanec, 1959, fig. 40).

The Herzog embryo was also described in Herzog MA. A contribution to our knowledge of the earliest known stages of placentation and embryonic development in man. (1909) Amer. J Anat., 9(3): 361-400.

This description cited in: Streeter GL. The developmental alterations in the vascular system of the brain of the human embryo. (1921) Contrib. Embryol., Carnegie Inst. Wash. 8:7-38.
Embryo used in: Florian J. The early development of man, with special reference to the development of the mesoderm and cloacal membrane. (1933) J. Anat., 67(2): 263-76. PMID 17104422
Other embryology papers presented at this 1916 meeting: Evans HM. and Bartelmez GW. A human embryo of seven to eight somites. (1917) Anat. Rec. 11: 355.

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A Comparison of the Herzog and Strahl-Beneke Embryos

Frederick Thomas Lewis
Frederick Thomas Lewis (1875-1951)

By Frederic T. Lewis

Harvard Medical School.

(Lantern) Presented at the 33rd Meeting of the American Association of Anatomists in New York (Dec 27-29, 1916).


The Herzog and Strahl-Beneke embryos are of particular value to embryologists since they are the youngest human embryos of which satisfactory drawings of serial sections have heretofore been published (22 sections of the Herzog embryo and 60 of the Strahl-Beneke specimen). Of the Peters embryo, apparently only a single section is thus available, which has been reproduced everywhere; and although 30 sections of the Bryce-Teacher specimen have bcen published, they are fragments defying interpretation, at least apart from the specimens themselves. Bryce and Teacher estimate that their embryo is three days younger, and Peters two days younger, than the Bencke specimen; but that these figures are merely approximations is indicated by the fact that Bryce and Teacher consider Peters embryo to be thirteen and one-half to fourteen and one-half days old on p. 53 of their work, but fourteen to fifteen days on p. 59. Although the difference in age of the four specimens under discussion is perhaps not greater than three days, thcre is the widest difference in the amount of information available about their structure. The Strahl-Beneke and Herzog embryos are the ones to which at present we must resort for an approximately adequate description.

Herzog’s embryo is not now in a good state of preservation and its reconstruction is in part a matter of restoration. Thus the detached tube in the body-stalk, which was originally intcrpretcd as an allantois, is clearly an amniotic duct. The place where it was torn off from the amnion can be definitely located. (This fundamental correction, reported at the 1913 meeting of this association, involves a change in labelling rather than any other modification of the model figured by the writer in Keibel and Mall’s Embryology, vol. 2.) The Strahl-Beneke embryo is in far better condition, and helps to explain the Herzog specimen, whereas the latter is the most interesting commentary on Strahl and Beneke’s important publication. This was appreciated by Strahl and Beneke who expressed regret that Herzog’s paper was received too latc for them to make a detailed comparison between his sections and their own, and they merely note that his sections differ in many respects very strikingly from theirs. We can now supply such a comparison and find that the embryos are so nearly alike that they may be said to establish the essential features of a certain early stage in hunian development. The conditions in younger human embryos are still subjects for diagram and conjecture.

Online Editor - Images of the embryos below are from other publications and do not appear in the above abstract.

Wax reconstruction of Herzog's embryo

Keibel Mall 2 227.jpg

Cite this page: Hill, M.A. (2024, April 23) Embryology Paper - A comparison of the Herzog and Strahl-Beneke embryos. Retrieved from

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