To the Editor:—
I should like to second the letter of Klein and Pollack (JAMA188:1017 [June 15] 1964) concerning the communication, "Psychological Deficits With Mitral Commissurotomy," by Herbert and Movius (JAMA187:767 [March 7] 1964). The effects of practice are manifested almost universally when the same or similar psychological tests are repeated. The lack of a control group makes the results of the study clearly inconclusive. If the conclusions of the authors lead to complacency on the part of surgeons and anesthesiologists, incalculable harm could result with the use of cardiopulmonary bypass.