The Father William Most Collection
The Presence of Christ
There are several kinds of presence of Christ: He is present where two or three are gathered in His name. He is present in the Sacraments, in that He brings about the effects of them. He is present in the word of Scripture.
But His presence in the Holy Eucharist is in a class by itself: It is the physical presence of His body, blood, soul and divinity, as means of the transmission of grace. The other presences are not nearly so great as this. He remains present as long as the appearances of bread and wine last. So after receiving Holy Communion, He will be present within the person as long as the appearances last. The amount of time can vary, but something like 15 minutes from the time of receiving would be a reasonable estimate. Therefore people should stay a bit after Mass for thanksgiving. To run out at once is to lack respect. Even if He is still presenting the ways indicated above, they are not in the same class as His physical presence in the Eucharist.