Wilhelm His invented a new kind of visual standard, a ‘normal plate’.
His arranged specimens in developmental order and selected appropriate representatives. This was far from trivial. He could not simply sort the embryos by time from fertilization, since this was not reliably known, so instead set up a special measure of length. For the variously shaped earliest specimens, he fell back on his judgement of overall form. Selecting normal specimens from material that, by its very origin in abortions, was suspected of abnormality was even harder. His could only compare his own and published descriptions among themselves as he drew and redrew, excluding venerable specimens and some undistinguished recent offerings from gynęcologists.
Though His began by setting up ‘stages’ of human development, he soon abandoned this system in favour of a series of ‘norms’. These were not, as for Soemmerring, the most perfect, but merely individuals he took to be characteristic, well preserved and well described. So though His faced fundamentally the same problems, he solved them in significantly differently ways. He called the resulting seriation a Normentafel or ‘normal plate’.
A drawing apparatus or ‘embryograph’. For His, exact drawings of whole embryos and sections were the foundation of all serious work. Committed to mechanical drawing aids, he found the standard combination of microscope and camera lucida unsuitable for the low magnifications (5–20 x) that embryological specimens required. So he replaced the microscope with lenses freely movable on a graduated retort stand. From the early 1880s Edmund Hartnack of Paris and Potsdam sold the apparatus as an ‘embryograph’. We see a drawing prism (top), objective lens, stage and mirror (bottom); the image was projected onto a drawing table. The embryograph was widely used, but Haeckel, defending himself against accusations of tendentious drawing, mocked His for reducing the morphologist to an automaton-like ‘embryographer’.
Embryograph, total height of c.45 cm, acquired from a Dr M. Abraham in 1942.
Historical Collections, National Museum of Health and Medicine, Armed Forces Institute of Pathology, Washington D.C.
A drawing apparatus or ‘embryograph’, late 1800s
Normal plate by Wilhelm His. His had his artist draw embryos from about the end of the second week to the end of the second month. The plate almost creates the impression of a single embryo at a succession of stages, but in fact brought together specimens from diverse medical encounters. The ninth figure shows embryo A.
Lithograph by C. Pausch from Wilhelm His, Anatomie menschlicher Embryonen, part 3: Zur Geschichte der Organe, Leipzig: Vogel, 1885, plate X. Border 46 x 33 cm.
By permission of the Syndics of Cambridge University Library.
Normal plate by Wilhelm His, 1885