Here is the applicable part of the Relatio:
Bishop Vincent Gasser, in his famous defense of papal infallibility (the Relatio) at the First Vatican Council, discussed the aspects of collegiality and community:
"We do defend the infallibility of the person of the Roman Pontiff, not as an individual person but as the person of the Roman Pontiff or a public person, that is, as head of the Church in his relation to the Church Universal . . .
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We do not exclude the cooperation of the Church because the infallibility of the Roman Pontiff does not come to him in the manner of inspiration or of revelation but through a divine assistance.
Therefore, the Pope, by reason of his office and the gravity of the matter, is held to use the means suitable for properly discerning and aptly enunciating the truth. These means are councils, or the advice of the bishops, cardinals, theologians, etc. Indeed the means are diverse according to the diversity of situations, and we should piously believe that, in the divine assistance promised to Peter and his successors by Christ, there is simultaneously contained a promise about the means which are necessary and suitable to make an infallible pontifical judgment.
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Finally we do not separate the Pope, even minimally, from the consent of the Church, as long as that consent is not laid down as a condition which is either antecedent or consequent. We are not able to separate the Pope from the consent of the Church because this consent is never able to be lacking to him.
Indeed, since we believe that the Pope is infallible through the divine assistance, by that very fact we also believe that the assent of the Church will not be lacking to his definitions since it is not able to happen that the body of bishops be separated from its head, and since the Church universal is not able to fail… "
"Note well. It is asked in what sense the infallibility of the Roman Pontiff is “absolute.” I reply and openly admit:** in no sense is pontifical infallibility absolute**, because absolute infallibility belongs to God alone, who is the first and essential truth and who is never able to deceive or be deceived. All other infallibility, as communicated for a specific purpose, has its limits and its conditions under which it is considered to be present. The same is valid in reference to the infallibility of the Roman Pontiff. For this infallibility is bound by certain limits and conditions. What those conditions may be should be deduced not “a priori” but from the very promise or manifestation of the will of Christ. Now what follows from the promise of Christ, made to Peter and his successors, as far as these conditions are concerned? He promised Peter the gift of inerrancy in Peter’s relation to the Universal Church: “You are Peter, and on this rock I will build my Church, and the gates of hell shall not prevail against it …” (Mt. 16:18). “Feed my lambs, feed my sheep” (Jn. 21:13-17).
Peter, placed outside this relation to the universal Church, does not enjoy in his successors this charism of truth which comes from that certain promise of Christ. Therefore, in reality, the infallibility of the Roman Pontiff is restricted by reason “of the subject,” that is when the Pope, constituted in the chair of Peter, the center of the Church, speaks as universal teacher and supreme judge: it is restricted by reason of the “object,” i.e., when treating of matters of faith and morals; and by reason of the “act” itself, i.e., when the Pope defines what must be believed or rejected by all the faithful. emphasis added
matt1618.freeyellow.com/treatise16.html
When you read the Relatio, you find Mardukm is completely and amply supported. The body of the Church cannot be separated from the head; nor the head from the body. Lumen Gentium is along the exact same lines as the Relatio.