To the Editor.—Thank you for allowing me to comment on the letter of Drs. Finkelstein and Mudd concerning transcriptions of my comments on their work1,2 made at the "Symposium on Treatment of Amino Acid Disorders." Discussants at symposia which are to be published in their entirety are usually afforded an opportunity to edit their transcribed remarks prior to publication. This was not true in the case of this symposium which comprised the Jan 1967 issue of the Journal. I am glad that I now can restore meaning to my comments which appear stripped of their comprehensibility.
Since we are working along parallel lines, I have studied the papers of Finkelstein and Mudd with great interest and care. I was quite aware that in their study of cystathioninuria and in their other published work1,2 pyriodoxal phosphate was added to the cystathionase assay system. The meaning I intended to