The Medium IS the Message?

 After being exposed to this quote by McLuhan for the second time in two semesters, I think I am starting to understand what he is trying to say...I say again...I think.  The concept in which he uses the electric light as an example makes total sense in interpreting what "the medium is the message" is saying.  Essentially, the light is the medium, without a message...unless it spells something out.  However, what "content" of the light may be different things.  It could be what the context of the message the light is spelling, or what the light may be illuminating... This is where I became a bit confused, but I understand now the angle McLuhan was going at.  I always understood the message as part of the content...but after thinking about it...you receive a message...and the content is what is in the message...so I guess, you can separate the two as separate entities.  ANYWAYS in saying that, the medium is the message that contain the content.  Another interesting idea in understanding what I said is seen on pg 205, McLuhan states, "Before the electric speed and total field, it was not obvious that the medium is the message.  The message, it seemed, was the 'content' as people used to ask what a painting was about."  This solidified my understanding a little bit more of what McLuhan was meaning when saying "the medium is the message".  So to easily break down what he is saying, the medium is the message because it is a tool in which content is delivered.  That's my understanding...