Paper - The human conceptus during the first two weeks of gestation

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Rock J. and Hertig AT. The human conceptus during the first two weeks of gestation. (1948) Amer. J. Obstet. Gynecol, 55: 6-17. PMID 18918949

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This historic 1949 paper describes early human development in week 1 and 2. Draft only.

See also: Rock J. and Hertig AT. Two human ova of the previous stage, having an ovulation age of about eleven and twelve days respectively. (1941) Contrib. Embryol., Carnegie Inst. Wash. Publ.525, 29: 127-156.

Rock J. and Hertig AT. Some aspects of early human development. (1942) Amer. f. Obstet. Gynecol, 44: 973-983.

Hertig AT. and Rock J. Two human ova of the pre-villous stage, having a developmental age of about seven and nine days respectively. (1945) Contrib. Embryol., Carnegie Inst. Wash. Publ. 557, 31: 65-84.

Hertig AT. and Rock J. On a normal human ovum not over 7.5 days of age. (1945) Anat. Rec. 91: 281.

Hertig AT. and Rock J. On a normal ovum of approximately 9 to 10 days of age. (1945) Anat. Rec. 91: 281.

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The Human Conceptus during the First Two Weeks of Gestation

John Charles Rock
John Charles Rock (1890-1984)
Arthur T Hertig
Arthur Tremain Hertig (1904-1990)

John Rock and Arthur T . Hertig

Free Hospital for Women, Brookline, Mass., Departments of Pathology, Obstetrics and Gynecology, Harvard Medical School and Department of Embryology, Carnegie Institution of Washington.


The youngest human embryo was conceived, not naturally in the Fallopian tube of its mother, but in a watch glass in the laboratory. It was the last of a series of almost 800 eggs. all recovered from ovarian tissue, of which 138 were exposed by Mrs. Miriam F. Menkin and me to human spermatozoa in about 1 c.c. of Ringer-Locke's Solution. After a pencil drawing was made of this two-cell individual, it was regrettably lost. A few days later , however, another egg similarly treated began its personal existence by changing from a single cell that had been part of the maternal tissue into a two-cell autonomous structure (Fig. 1, A.). Because none had been seen to do likewise without spermatozoa, and there were spermatozoa within the zona pellucida, it was probable that this two-cell organism is the result of conjugation of the male and female components. Some weeks later, similar procedures resulted in the production of two ova in the three-cell stage.

Cite this page: Hill, M.A. (2024, June 21) Embryology Paper - The human conceptus during the first two weeks of gestation. Retrieved from

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