overstating my indebtedness to him when I say that if it had not been for the assistance which I have derived from his published papers, from his personal collaboration in experiment, and from his criticism, this book would never have taken shape.
To Miss Gertrude Woodward I have to express my grateful acknowledgments for the skill and patience which she devoted to the preparation of the illustrations.
I am indebted also to my friends, Mr. J. W. Gordon, Mr. Maynard Smith, F.R.C.S., and Lieut.-Col. W. B. Leishman, R.A.M.C., for help in connexion with the illustrations, and to Messrs. Carl Zeiss for the blocks of Figs. 2, 3 and 4 on Plate XII.
Lastly, I would ask my publishers—Messrs. Constable & Co.—to accept my very sincere thanks for the generous way in which they have fallen in with my many onerous suggestions in connexion with the production of this work.
ST. MARY'S HOSPITAL,
LONDON, W.
