This had often been done before.

It remained to devise a way of keeping these records, so that the markings might all be removed from the skin, and new explorations made over the same surface.

This was necessary in order to see whether the results secured were always the same.

The theory that there were certain nervous endings in the skin corresponding to the little points required that each spot should be in exactly the same place whenever the experiment was repeated.
[Footnote 3: Mr.J.F.Crawford, graduate student.] Mr.C.made a number of so-called "transparent transfer frames." They are rectangular pieces of cardboard, with windows cut in them.

The windows are covered with thin architect's paper, which is very transparent.