First of all, RIP Professor Morgan. He passed away earlier this year (2008). From the NORML.com website:

Dr. John P. Morgan was a physician and professor of pharmacology at the City University of New York Medical School. He graduated from the University of Cincinnati College of medicine in 1965. Following training in internal medicine (at Syracuse) and clinical pharmacology (at John Hopkins University and the University of Rochester), he began a career in academic pharmacology and medicine at the University of Rochester. He began his position at City College in 1977, where his teaching included the topics of pharmacology, clinical pharmacology and drug policy. His book, Marijuana Myths, Marijuana Facts (The Lindesmith Center, New York, 1997) reviews the latest scientific and medical research and debunks the common marijuana myths.
Dr. Morgan published approximately 100 articles, book chapters and books, largely focused on the clinical pharmacology of psychoactive drugs. His research and writing involved issues such as urine testing in the American workplace, medical marijuana, the socio-pharmacology of crack-cocaine, alcohol prevalence during national prohibition, and physician prescribing practices.

Dr. Morgan was a member of numerous professional associations, including the American Society of Addiction Medicine, the American Society of Clinical Pharmacology and Therapeutics, and the American Council on Science and Health, and he served on the advisory board of the Drug Policy Alliance.

and here is a video of him speaking about weed.