Typescript letter with autograph postscript written on Department of Physical Chemistry, Harvard Medical School letterhead and signed by Dr. E. Carrasco-Formiguera. A diabetic doctor from Barcelona, Spain presently at the Department of Physical Chemistry in the Harvard Medical School, Dr. Carrasco-Formiguera attended the Yale conference in which Macleod spoke of the Toronto discovery. He writes for more details explaining that he understands Macleods desire to refuse to make known any data that might lead to any misuse of your pupils discovery but that he has a very severe case in Barcelona.