Dr. Roy R. Grinker, M.D., Chicago, comments:

Drs. Engel and Reichsman are correct in assuming that I was referring to a memorandum prepared by Dr. Engel and circulated among his colleagues. I had overestimated in reading their report the proof which I now see is only an hypothesis. They are to be congratulated for not accepting the finality of their statements and are planning to continue their most excellent and stimulating work. It is very rare in these days to find authors who reject a generous evaluation of their work—an evaluation which bespeaks my confidence in their scientific activities. It is my belief that their letter published above adds a great deal to an understanding of the complexities of the problems concerned with identification.