Paper - A Human Embryo with Seven Pairs of Somites Measuring about 2 mm in Length
Embryology - 25 Apr 2024    Expand to Translate
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Dandy WE. A Human Embryo with Seven Pairs of Somites Measuring about 2 mm in Length. (1910) Vol. 10
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A Human Embryo with Seven Pairs of Somites Measuring about 2 mm in Length
By
Walter E. Dandy.
From The Anatomical Laboratory, Johns Hopkins University.
With 6 Plates.
Among the youngest human embryos and one of the youngest in Professor Mall’s collection, Embryo No. 391, which he has very kindly permitted me to reconstruct and describe. In general development this embryo is almost identical with, probably a trifle older than, the Kroenier-Pfannestiol embryo, Klb, which measures 1.8 mm. and has six ‘pairs of somites. It is older than E’rernod’s embryo measuring 1.3 mm., Grraf Spee’ s Gle 1.54 mm., and Embryo Frassi 1.17 mm., in the order named. It is younger than the embryos of Unger and Bulle, of 9 and 14 somites respectively, Eternod’s 2.1 mm. embryo, and embryos XLIV (Eff), LXVIII (Lg. 2.15 mm.), VI (B. R. 2.2 mm.) and VII (E 2.1 mm.) of His.
This very rare specimen came into Professor Mall’s possession through the kindness of Dr. R. W. Pearce, of Albany, New York, with the following history from the physician who handed the specimen to him. “The woman had passed her period about two weeks when she performed an abortion with a stick about 8 inches long, which she whittled out for the purpose. This she passed into the uterus and 24 hours later this specimen was aborted. Her purpose in calling me was to see if her object had been attained. I have kept the specimen two years in a bottle of weak formaldehyde.”
Upon receipt the following measurements were. made by Professor Mall; ovum 162: 14x12 mm., embryo about 2 mm. The specimen was placed in fresh formalin, stained with alum-cochineal-eosin, imbedded in paraffin and cut into serial sections 10 microns in thickness.
From these sections (163 in number, excluding the bauehstiel), the embryo was reconstructed upon a scale of 200 magnification, giving the model a total length of 32.6 cm. A shrinkage space between the layers of tissue aided materially in the reconstruction without sacrificing tissue. The model is so constructed that every detail may be exposed by cuts and windows.
Upon presentation of an embryo the question naturally arises, is it normal? The history of a mechanical abortion points very strongly toward a normal embryo. It compares very closely with the few other known embryos of this period. The tissues, including the chorion, are excellently preserved and show no degenerative changes.
Age
From the history that the menstrual period passed about two weeks, the age of 13-14 days would fit very nicely into the conventional Reichert—His theory of fertilization and age of embryos. Recent observations however by Mall in 1000 cases with menstrual history have shown that we underestimate the age of young embryos, on an average about 10 days, that fertilization is not restricted to the period immediately before the menstrual period, but may occur at any time in the intermenstrual period. Bryce and Teacher also came to the same conclusions and illustrate this in a well constructed diagram of the menstrual cycle. This obviates the remarkable distortion which has been necessary to harmonize age with size and progress of development, and makes the human embryo much less precocious in its development. In conformity to the above observations the true age of this embryo is probably about 24 days, which would make the time of fertilization occur about ten days before the time for onset of lapsed menstrual period or about eighteen days after beginning of the last menstrual period.
The Adnexa
Chorion. The chorionic membrane is about 0.1 mm. thick, and is covered with many branching villi varying in size up to 1.25 mm. in length and 0.1 mm, in thickness. These villi are more numerous at the point of attachment of the bauchstiel and gradually fade away on all sides until finally a clear zone results from their absence on the opposite pole.
Cite this page: Hill, M.A. (2024, April 25) Embryology Paper - A Human Embryo with Seven Pairs of Somites Measuring about 2 mm in Length. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_A_Human_Embryo_with_Seven_Pairs_of_Somites_Measuring_about_2_mm_in_Length
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
