Paper - Observations upon Young Human Embryos

James Thomas Wilson

Challis Professor of Anatomy in the University of Sydney, Australia.

<pubmed>17233002</pubmed>| PMC1288949

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Part 1

The appearance in recent years of Keibel and Mall's Manual of Human Embryology (1), following upon Keibel and Elze's Normentafein (2), marked an epoch in the formulation of our knowledge of specifically human development.

The comprehensive summary there offered of our knowledge of the earlier human ontogenetic processes provided for the firsttime a more or less connected account of these phenomena, but it also served to accentuate the still very sketchy and incomplete character of that knowledge.

Much of our belief in regard to the method of establishment of the human blastocyst is stil quite hypothetical, even if probable; and as regards the appearance of the earliest rudiments of the body itself, our knowledge isbased on a very few human specimens separated by intervals which it is important to fill in with the aid of intermediate or allied stages.

In the present paper I propose to give an account of the three youngest human embryos in my collection.

Previous writers have described and figured specimens of a stage of development more or less similar to those exhibited by the two older of the embryos which form the subject of this communication. Nevertheless, well-preserved specimens, of ages nearly corresponding to these, are of such comparative rarity that for some time to come it will still be desirable to have accurate records published of the form and structure of any that may become available for detailed examination. As a matter of fact, no two specimens hitherto described, however apparently similar in stage of development, have proved to be precisely identical in detail. It will appear in the course of the paper that each of the individual embryos under consideration presents features entitling it to independent description.

A more special interest attaches to the youngest of the three specimens, inasmuch as it would seem to exhibit a phase of development hitherto unrepresented in the records of early human embryos.

It possessed probably two, possibly three, pairs of somites, and may thus be determined as occupying a position in the gap between stages 2 and 3 of Keibel and Elze's Norrnentafel. These stages are represented respectively by Spee's embryo " Gle " (3), and the Kroemer-Pfannenstiel embryo " Klb."

Hitherto, or as far as I am aware, no human embryo has been recorded as exhibiting a smaller number of somites than five (in " Klb ").

I am inclined to believe that the embryo "E,"No.1 of His 'Normentafel (4), would have turned out to be of very similar character to that now about to be described, inspire of the somewhat greater length of the former (21 mm. as against 1-68 mm.).

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History of the Human Embryo "H3"