Quote Originally Posted by birdgirl73
You absorb the THC and other cannabinoids in smoked cannabis through a transaction in the tiny air sacks of your lungs, which is the furthest point the smoke travels to in your respiratory system. All your pal could remotely be spitting out would be traces of resin or particulate matter on his tongue. It might contain microscopic amounts of THC if you analyzed it in a lab, but he's not really wasting anything good or lessening an opportunity for a better high by spitting.
I could be wrong but my theory contradicts this one so I thought I would add this in.

I believe it is actually the large ventricles in your lungs that marijuana goes through. This is the oposite of ciggarettes and why you (well theoreticaly) can't get emphysyma and other lung related illnesses from cannabis. The tobacco attacks the small ventricles(wrong word?) and makes it harder to breathe and cuases emphysyma and all sorts of bad stuff.:rastasmoke: