Hence too we see, when comparing the Mass with the sacrifice of our Lord, how aptly the Council declared: "For the Victim is one and the same, the same now offering by the ministry of priests, who once offered Himself on the Cross, only the manner of offering being different. (ibid.,). For the difference between our offering and the offering of Christ is this, that ours is altogether bloodless, while the offering of Christ on the Cross was in blood in the manner shown. Nevertheless there was not one offering on the Cross and another in the Supper, but it was numerically one same offering: made ritually in the Supper, continued morally on the Cross; all this because of the identity of the Priest and the Victim,—a rational Victim whose constant will in suffering unto death was none other than the continued will of the Priest faithful in sacrifice to the end. Moreover in the Supper Christ offered without us, in the Mass He offers through us; hence again the manner of offering is different.In the third place, if we compare the Mass with the Supper, note with what truth Christ said Do this, namely, do what I have done; for apart from the difference of time it is absolutely the same. For the Supper looked to the immolation as future, the Mass looks to it as past. Hence it is that the Supper looked forward to the Passion, which the Mass presupposes. Therefore the sacrifice celebrated in the Supper was not completed immediately upon the consecration (and transubstantiation), but it continued on until Christ died. Our sacrifice of the Mass on the other hand, is completed immediately upon the consecration, because the immolation has already taken place. The difference between the Supper and the Mass therefore, is the difference between the offering of a victim to be immolated and the offering of a victim already immolated. This does not imply any particular excellence of the Mass as compared with the Supper, as if the Mass were in itself more complete as sacrifice than the Supper; for as we have said the Supper looks forward, the Mass presupposes. The Mass presupposes something which the Supper did not presuppose (for it had not yet taken place). The Supper looked forward to something to which the Mass does not look forward (for it has taken place). But each has its own complement in the immolation of the Passion—though differently, because of the difference in time.
Ummnnhhh...thanks.
The part about 'completion of the Sacrifice' would seem to be quite significant.
ninenot wasn't making a distinction. He was categorically denying the last supper was mass. The Catholics I know, who are my age, learned the action of Mass consisted in Jesus offering Himself as (priest and victim) as a sacrificial offering of propitiation - which is what happend at the last supper and which Trent, ect ect, taught was when the Mass was instituted.