Talk:Embryology History - Robert Meyer

Thompson P. Description of a human embryo of twenty-three paired somites. (1907) J Anat Physiol, 41(3):159-71. PMID 17232726

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 thickness. When the plates had been cut and laid in position, it was found, owing probably 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.