When Dr. Cook, who has the thankless task of organizing the papers and discussion of this meeting, told me I had let him down because I had not secured one of the most distinguished surgeons in the country, Mr. Jefferson, he put it to me that the least I could do was to fill in the gap. I was puzzled as to what to say until Prof. MacDonald gave me a clue, and instead of talking on physiology and anatomy, which, after all, you probably know better than I do, I propose to give you a few general considerations which seem to make for the defence of an operation such as this against Prof. MacDonald's criticism.