If you do take it orally, consider that the time release on it is HIGHLY effective. The effects can easily last for 12-14 hours. And even if you're never entirely all that high, after that much time of your body just getting hit and hit, you'll probably wake up in the morning high as hell and sick as a dog puking.
And as I just said in another thread, if you're not opiate tolerant 100mgs is a bit much. Taken orally, you do not want to go over 50mgs at most if this is the case.
And the above poster probably has little or no experience with morphine sulfate. Unlike oxycodone, it is NOT very effective to snort. Especially not MSContin. It will also burn like hell and because the time release components are so well attached to the morphine particles, not much will be asorbed. You've got a decent dose, it will work fine orally. If you only had 15mgs, that would be a different story, though.