Paper - Description of a Human Embryo of Twenty-three Paired Somites

Peter Thompson

<pubmed>17232726</pubmed>| PMC1289111

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Introduction

THE embryo which forms the basis of this work came from Dr Robert Meyer's collection in Berlin. Sent to Professor Keibel, who was accumulating material for his forthcoming Normentafeln of human embryos, the specimen was most kindly lent to me with the object of making a model whilst I was at the Anatomical Institute in Freiburg during the summer of 1906. Working with this specimen, I had an excellent opportunity of becoming acquainted with the reconstruction of embryos by the wax-plate method, as carried out so successfully in that University.

The embryo, obtained at an operation, was recorded as 2.5 mm. long, and was cut transversely into 488 sections, each 5 , in thickness, and stained with borax-carmine. In making the model, every other section was drawn, enlarged 100 diameters, and the wax plates were made 1 millimetre in thick- ness. Whentheplateshadbeencutandlaidinposition,itwasfound, owingr prol)ably to the hot weather and the weight of wax, that the total height of the model was only 220 millimetres, and, in order to correct the error, 24 additional wax plates were made, duplicates of every tenth section, and introduced into the series. In this way the total length of the model was brought up to 244 millimetres, corresponding to the 244 sections used, which indicates a shortage of less than 3 per cent, when compared with the 250 millimetres, the absolutely accurate measurement which the enlargement should have been, taking the length of embryo as 25 min. The difference is probably due to a slight shrinkage, which would most probably occur in preparing the specimen for cutting. It may be stated here that the embryo is histologically in excellent condition, mitosis being readily observed in the multiplying cells, and there seems no valid reason for doubting that the specimen is a normal one. Inaddition to the model of the whole embryo and its yolk sac, other models were made of special organs, namely, the heart and its endothelial tube, the brain, a part of the alimentary canal, and the septum transversum.

It may be noted that the embryo described in this paper resembles in many ways His's embryo Lg., which was2-15mm. in length and estimated to be about fifteen days old.

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Cite this page: Hill, M.A. (2024, June 2) Embryology Paper - Description of a Human Embryo of Twenty-three Paired Somites. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_Description_of_a_Human_Embryo_of_Twenty-three_Paired_Somites

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