Understanding Media

Marshall McLuhan's Understanding Media essay explores the medium of the media. I need some clarification on McLuhan's view that the medium is more influential than the message of the medium. I have questions about McLuhan's finer points. Is there ever anything that is the message, or is it only the medium that we see? Does culture ever really change, or does it just shift? What happens when technology significantly alters the human body? Will society stop shifting and become something new for the first time? Marshall McLuhan's work connects anthropology, science, media studies, and an understanding of new technologies, and it still seems modern after four decades.