I - Defects of the Missing
1. The priest who is to celebrate Mass should take every precaution to make sure that none of the things required for celebrating the Sacrament of the Eucharist is missing. A defect may occur with regard to the matter to be consecrated, with regard to the form to be observed and with regard to the consecrating minister. There is no Sacrament if any of these is missing: the proper matter, the form, including the intention, and the priestly ordination of the celebrant. If these things are present, the Sacrament is valid, no matter what else is lacking. There are other defects, however, which may involve sin or scandal, even if they do not impair the validity of the Sacrament.
II - Defects of the matter
2. Defects on the part of the matter may arise from some lack in the materials required. What is required is this: bread made from wheat flour, wine from grapes, and the presence of these materials before the priest at the time of the Consecration.
III - Defect of bread
3. If the bread is not made of wheat flour, or if so much other grain is mixed with the wheat that it is no longer wheat bread, or if it is adulterated in some other way, there is no Sacrament.
4. If the bread has been made with rose-water or some other distillation, the validity of the Sacrament is doubtful.
5. If the bread has begun to mold, but it is not corrupt, or if it is not unleavened according to the custom of the Latin Church, the Sacrament is valid but the celebrant is guilty of grave sin.
6. If the celebrant notices before the Consecration that the host is corrupt or that it is not made of wheat flour, he is to replace that host with another, make the offering at least mentally and continue from where he left off.
7. If he notices this after the Consecration, or even after having consumed the host, he is to put out another host, make the offering as above and begin from the Consecration, namely from the words Qui pridie quam pateretur. If he has not consumed the first host, he is to consume it after taking the Body and the Blood, or else reserve it somewhere with reverence. If he has already consumed the first host, he is nevertheless to consume the one that he has consecrated, because the precept of completing the Sacrament is more important than the precept of fasting before Communion.
8. If this should happen after the Blood has been consumed, not only should new bread be brought, but also wine with water. The priest should first make the offering, as above, then consecrate, beginning with the words Qui pridie. Then he should immediately receive under both species and continue the Mass, so that the Sacrament will not remain incomplete and so that due order will be observed.
9. If the consecrated host disappears, either by some accident such as a gust of wind or by some animal's taking it, and it cannot be found, then another is to be consecrated, beginning from the Qui pridie quam pateretur, having first been offered as above.
10. In the cases referred to in paragraphs 5-9 above, the elevation of the Sacrament is to be omitted, and everything is to be done so as to avoid, as far as possible, any scandal or wonderment on the part of the faithful.
IV - Defect of wine
11. If the wine has become mere vinegar, or is completely bad, or if it has been made from sour or unripe grapes, or if so much water has been mixed with it that the wine is adulterated, there is no Sacrament.
12. If the wine has begun to turn to vinegar or to become corrupt, or if it is souring, or if it is unfermented, being made from newly pressed grapes, or if it has not been mixed with water, or if it has been mixed with rose-water or some other distillation, the Sacrament is valid, but the celebrant is guilty of grave sin.
13. If the celebrant notices before the consecration of the Blood, even if the Body has already been consecrated, that there is no wine in the chalice, or no water, or neither wine nor water, he should immediately put in wine and water, make the offering as above and consecrate, beginning with the words Simili modo, etc.
14. If after the words of the Consecration he notices that there was no wine in the chalice, but only water, he is to pour the water into some vessel, put wine and water into the chalice and consecrate, starting again from the words Simili modo, etc.
15. If he notices this after consuming the Body, or after drinking the water in question, he is to set out another host to be consecrated, together with wine and water in the chalice, offer both, consecrate them and consume them, even though he is not fasting.
16. In the cases referred to in paragraphs 13-15 above, the elevation of the Sacrament is to be omitted, and everything is to be done so as to avoid, as far as possible, any scandal or wonderment on the part of the faithful.
17. If he finds out, before or after the Consecration, that the wine is completely vinegar or otherwise corrupt, he is to follow the same procedure as above, as if he were to find that no wine had been put into the chalice, or that only water had been put in.
18. If the celebrant remembers before the consecration of the chalice that there was no water added, he is to put some in at once and say the words of the Consecration. If he remembers this after the consecration of the chalice, he is not to add any water, because the water is not necessary to the Sacrament.
19. If a defect either of bread or of wine is discovered before the consecration of the Body, and the material needed cannot be obtained in any way, the priest should not continue any further. If after the consecration of the Body, or even of the wine, a defect in either species is discovered, and the material needed cannot be obtained in any way, then the priest should continue and complete the Mass if the defective material has already been consecrated, omitting the words and signs that pertain to the defective species. But if the material needed can be obtained with some little delay, he should wait, in order that the Sacrament may not remain incomplete.
V - Defects of the form
20. Defects on the part of the form may arise if anything is missing from the complete wording required for the act of consecrating. Now the words of the Consecration, which are the form of this Sacrament, are:
HOC EST ENIM CORPUS MEUM, and HIC EST ENIM CALIX SANGUINIS MEI, NOVI ET AETERNI TESTAMENTI: MYSTERIUM FIDEI: QUI PRO VOBIS ET PRO MULTIS EFFUNDETUR IN REMISSIONEM PECCATORUM If the priest were to shorten or change the form of the consecration of the Body and the Blood, so that in the change of wording the words did not mean the same thing, he would not be achieving a valid Sacrament. If, on the other hand, he were to add or take away anything which did not change the meaning, the Sacrament would be valid, but he would be committing a grave sin.
21. If the celebrant does not remember having said the usual words in the Consecration, he should not for that reason be worried. If, however, he is sure that he omitted something necessary to the Sacrament, that is, the form of the Consecration or a part of it, he is to repeat the formula and continue from there. If he thinks it is very likely that he omitted something essential, he is to repeat the formula conditionally, though the condition need not be expressed. But if what he omitted is not necessary to the Sacrament, he is not to repeat anything; he should simply continue the Mass.
VI - Defects of the minister
22. Defects on the part of the minister may arise with regard to the things required in him. These are: first of all the intention, then the disposition of soul, the bodily disposition, the disposition of vestments, the disposition in the rite itself with regard to the things that may occur in it.
VII - Defect of intention
23. The intention of consecrating is required. Therefore there is no consecration in the following cases: when a priest does not intend to consecrate but only to make a pretense; when some hosts remain on the altar forgotten by the priest, or when some part of the wine or some host is hidden, since the priest intends to consecrate only what is on the corporal; when a priest has eleven hosts before him and intends to consecrate only ten, without determining which ten he means to consecrate. On the other hand, if he thinks there are ten, but intends to consecrate all that he has before him, then all will be consecrated. For that reason every priest should always have such an intention, namely the intention of consecrating all the hosts that have been Placed on the corporal before him for consecration.
24. If the priest thinks that he is holding one host but discovers after the Consecration that there were two hosts stuck together, he is to consume both when the time comes. If after receiving the Body and Blood, or even after the ablution, he finds other consecrated pieces, large or small, he is to consume them, because they belong to the same sacrifice.
25. If, however, a whole consecrated host is left, he is to put it into the tabernacle with the others that are there; if this cannot be done, he is to consume it.
26. It may be that the intention is not actual at the time of the Consecration because the priest lets his mind wander, yet is still virtual, since he has come to the altar intending to do what the Church does. In this case the Sacrament is valid. A priest should be careful, however, to make his intention actual also.
VIII - Defects of the disposition of soul
27. If a priest celebrates Mass in a state of mortal sin or under some ecclesiastical penalty, he does celebrate a valid Sacrament, but he sins most grievously.
IX - Defects of the disposition of body
28. If a priest has not been fasting for at least one hour before Communion, he may not celebrate. The drinking of water, however, does not break the fast.
29. The sick, even though they are not bed-ridden, may take non-alcoholic liquids as well as true and proper medicine, whether liquid or solid, before the celebration of Mass, without any time limit.
30. Priests who can do so are earnestly invited to observe the ancient and venerable form of the Eucharistic fast before Mass.
X - Defects occurring in the celebration of the rite itself
31. Defects may occur also in the performance of the rite itself, if any of the required elements is lacking, as in the following cases: if the Mass is celebrated in a place that is not sacred, or not lawfully approved, or on an altar not consecrated, or not covered with three cloths; if there are no wax candles; if it is not the proper time for celebrating Mass, which is from one hour before dawn until one hour after noon under ordinary circumstances, unless some other time is established or permitted for certain Masses; if the priest fails to wear some one of the priestly vestments; if the priestly vestments and the altar cloths have not been blessed; if there is no cleric present nor any other man or boy serving the Mass; if there is not a chalice, with a cup of gold, or of silver with the inside gold-plated; if the paten is not gold-plated; if both chalice and paten are not consecrated by a bishop; if the corporal is not clean (and the corporal should be of linen, not decorated in the middle with silk or gold; and both corporal and pall should be blessed); if the priest celebrates Mass with his head covered, without a dispensation to do so; if there is no missal present, even though the priest may know by heart the Mass he intends to say.
32. If, while the priest is celebrating Mass, the church is violated before he has reached the Canon, the Mass is to be discontinued; if after the Canon, it is not to be discontinued. If there is fear of an attack by enemies, or of a flood or of the collapse of the building where the Mass is being celebrated, the Mass is to be discontinued if it is before the Consecration; if this fear arises after the Consecration, however, the priest may omit everything else and go on at once to the reception of the Sacrament.
33. If before the Consecration the priest becomes seriously ill, or faints, or dies, the Mass is discontinued. If this happens after the consecration of the Body only and before the consecration of the Blood, or after both have been consecrated, the Mass is to be completed by another priest from the place where the first priest stopped, and in case of necessity even by a priest who is not fasting. If the first priest has not died but has become ill and is still able to receive Communion, and there is no other consecrated host at hand, the priest who is completing the Mass should divide the host, give one part to the sick priest and consume the other part himself. If the priest has died after half-saying the formula for the consecration of the Body, then there is no Consecration and no need for another priest to complete the Mass. If, on the other hand, the priest has died after half- saying the formula for the consecration of the Blood, then another priest is to complete the Mass, repeating the whole formula over the same chalice from the words Simili modo, postquam cenatum est; or he may say the whole formula over another chalice which has been prepared, and consume the first priest's host and the Blood consecrated by himself, and then the chalice which was left half-consecrated.
34. If anyone fails to consume the whole Sacrament aside from cases of necessity of this kind, he is guilty of very grave sin.
35. If before the Consecration a fly or spider or anything else falls into the chalice, the priest is to pour out the wine in a suitable place, put other wine into the chalice, add a little water, offer it, as above, and continue the Mass. If after the Consecration a fly or something of the kind falls into the chalice, he is to take it out, wash it with wine, burn it after the Mass is over, and throw the ashes and the wine which was used for washing into the sacrarium.
36. If something poisonous falls into the chalice after the Consecration, or something that would cause vomiting, the consecrated wine is to be poured into another chalice, with water added until the chalice is full, so that the species of wine will be dissolved; and this water is to be poured out into the sacrarium. Other wine, together with water, is to be brought and consecrated.
37. If anything poisonous touches the consecrated host, the priest is to consecrate another and consume it in the way that has been explained, while the first host is to be put into a chalice full of water and disposed of as was explained regarding the Blood in paragraph 36 above.
38. If the particle of the host remains in the chalice when he consumes the Blood, he is to bring it to the edge of the cup with his finger and consume it before the purification, or else he is to pour water in and consume it with the water.
39. If before the Consecration the host is found to be broken, it is to be consecrated anyway, unless the people can see plainly that it is broken. But if there may be scandal for the people, another host is to be taken and offered. If the broken host has already been offered, the priest is to consume it after the ablution. If the host is seen to be broken before the offerings however, another complete host is to be taken, if this can be done without scandal and without a long delay.
40. If the consecrated host falls into the chalice, nothing is to be repeated on that account, but the priest is to continue the Mass, performing the ceremonies and making the usual signs of the Cross with the part of the host that is not moistened with the Blood, if he can conveniently do so. But if the entire host has become wet, he is not to take it out; he is to say everything as usual, omitting the signs of the Cross that pertain to the host alone, and he is to consume the Body and the Blood together, signing himself with the chalice and saying: Corpus et Sanguis Domini nostri, etc.
41. If the Blood freezes in the chalice in winter time, the chalice should be wrapped in cloths that have been warmed. If this is not enough, it should be placed in boiling water near the altar until the Blood melts, but care should be taken that none of the water gets into the chalice.
42. If any of the Blood of Christ falls, if it is only a drop or so, nothing need be done except to pour a little water over the spilled drops and dry it afterwards with a purificator. If more has been spilled, the corporal or the altar cloth or other place is to be washed in the best way possible, and the water is then to be poured into the sacrarium.
43. If, however, all the Blood is spilled after the Consecration, the little that remains is to be consumed, and the procedure described above is to be followed with the rest which has been spilled. But if none at all remains, the priest is to put wine and water into the chalice again and consecrate from the words Simili modo, postquam cenatum est, etc., after first making an offering of the chalice, as above.
44. If anyone vomits the Eucharist, the vomit is to be gathered up and disposed of in some decent place.
45. If a consecrated host or any particle of it falls to the ground or floor, it is to be taken up reverently, a little water is to be poured over the place where it fell, and the place is to be dried with a purificator. If it falls on clothing, the clothing need not be washed. If it falls on a woman's clothing, the woman herself is to take the particle and consume it.
46. Defects may occur in the celebration of the rite itself also if the priest does not know the rites and ceremonies to be observed, all of which have been fully described in the above rubrics.