The text is organized into what have been tested and found to be serviceable assignment units short chapters which may also be welcome to the general reader. Chapters 21 to 24 are by Dr. S. W. Williston, of the Uni versity of Chicago. Acknowledgment is made of the cour tesy of the American Book Company in connection with the use of illustrations that are on pages 95, 96, 101, and 107.