My heaviest obligation is to Dr. Adolf Meyer and to the staff of the Phipps Psychiatric Clinic before whom the manuscript was read as it was prepared. In numerous instances, under the kindly criticism received there, the text has been altered for the better. Captain H. M. Johnson, Dr. K. S. Lashley, Dr. J. L. Ulrich and Dr. N. D. C. Lewis have given generously of their time in reading the manuscript and proof. Each one has made helpful suggestions. I am greatly indebted to Prof. Max Broedel of the Art Department of the Johns Hopkins Medical School and to two of his assistants, Miss G. L. Meakin and Miss A. Motter, who, under his direction, made the excellent drawings of the nervous system after Dr. Florence Sabin had kindly made the dissections. Miss Meakin also made the drawings of the larynx after Dr. Warren Lewis had placed the material at our disposal. Dr. Samuel M. Burka has assisted me greatly in the preparation of the cuts and photographs of the infants.
In 1917, upon recommendation of Dr. J. McK. Cattell, the sum of one hundred dollars was appropriated by the Committee on Grants for Research of the American Association for the Advancement of Science for my assistance in studying the development of reflexes and instincts in infants. The expenses for the genetic work summarized in the text were defrayed in part by the above grant. I wish to make a grateful acknowledgment for this aid.
Finally, I have borrowed generously from many authors. Where the material has been often quoted in the past I have made no reference to the author. Where it is of the research type I have usually put the author's name in parentheses with no further reference. The student hungering for further work cannot be too early trained to use the Psychological Index.