To the Editor:—My attention has been called by Dr. Rudolph Matas, of New Orleans, to two historical errors which appear in my article, "The Negative Chamber in Open Pneumothorax: A Personal Experience," in the July issue of the Archives of Surgery. I stated, page 134, that "the importance of preventing this physical phenomenon was fully realized by Dr. Matas, more than twenty years ago, when, as one of the pioneers in the field of thoracic surgery in America, he had his assistant, Dr. Parham of New Orleans, excise a tumor of the chest wall with the help of a differential pressure apparatus, the Fell-O'Dwyer combination, as modified by Matas." The fact is that Dr. Matas and Dr. Parham have been connected with the same hospitals and have served in them, contemporaneously, as colleagues, with the same rank and always in charge of separate and independent services. Dr. Parham, therefore,