Excluding an embryo. The story of the embryo it took His most effort to exclude shows how open human embryology still was when he began work. In 1875 an anatomy professor, Wilhelm Krause, had described a human embryo as supporting Haeckel against His. For five years embryologists debated the possibility that the embryo was abnormal, but in 1879 His announced that it was not human at all, but a chick. Even then, Krause fought on and others continued to offer alternative explanations. The matter was decided only in 1882, when anatomists gathered to view the famous object. They declared it a bird, but that it was a chick they could not say; it might just as well have been a duck, a goose—or a turkey.

Setting standards

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’, late 1800s


Normal plate by Wilhelm His, 1885