On measuring human embryos

In looking over the literature on human embryology I find that it is not always easy l o determine the size and the degree of development of embryos, under consideration, partly on account of the lack of uniformity in measuring specimens and partly because it is not always stated how the measurements were taken.Obstetricians uniformly give as the standard measurement the greatest length of the fetus after it has been straightened more or less, and this measurement is a most useful one for it can be compared directly with the standing height after birth.This standard measurement is used quite frequently by embryologists, Toldt being one of the most recent who has employed it, but on account of the difficulty in making it upon young specimens without injuring them, Arnold and many others, including His, measured young embryos from the top of the head to the breech.This gave us the well known vertex-breech measurement, which corresponds w-i th the sitting height after birth.To these two measurements His has added a third, which he makes from the projection on top of the neck (over the medulla) to the breech, the neck-breech or Nackenlinie, which is a very useful measurement for embryos of the first and second months; in general it measures the length of the spinal column.However, from my own experience, as well as from that of others, this measurement is difficult to make accurately and therefore it has not proved to be of general value.During the past few years I have remeasnred all of the human embryos THE ANATOMICAL RECORD.--NO.6.