* * * * *
Transcriber's Notes:
Obvious typographical errors were repaired. Hyphenation variants used
equally were retained (back-bone and backbone, thread-like and
threadlike).
Original had chapter title pages before the start of each chapter,
resulting in duplication of chapter titles. Those duplications have
been removed.
Original contents erroneously indicated Lecture VI began on page 217.
This has been corrected to page 219.