‘Λόγος’ as soon as we are led, by way of other sayings of Heraclitus’s, to grasp in one essential glimpse the fundamental features of being as experienced in a Greek way.
(Regarding the connection between fire, light, and measure, see fragment 30. Regarding the relationship of the One (which, as being, unites all beings) with light and what lightens, see fragment 64.)
When fragment 45 says that the soul of the human has a far-reaching λόγος, and when fragment 72 says that humans are most of all turned toward the Λόγος in a manner that bears, the two fragments say the same and designate that in which the drawing-in drawing-out (i.e., the soul) is engaged. Because the soul of the human has a far-reaching λόγος that has reached far—which, however, as dictated by the necessity of ὁμολογεῖν, points  to the Λόγος and is both sublated and grounded within it—we will only ever experience, know, and consummate the essence of human λόγος to the degree to which the Λόγος itself presences in the human’s compliant attendance to it.
For the sake of all further efforts to think-after λόγος as Heraclitus conceived it, in order to thereby arrive at an originary ‘logic,’ we must heed the directive that arises from out of what has already been said: namely, we must attempt to formulate a definition of the essence of the Λόγος to the highest possible degree of precision before turning to the human λόγος. But how are we to direct our gaze toward the essence of the Λόγος if the human λόγος, by which we are carried and led, is not executed properly in the manner of a ὁμολογεῖν? We cannot take ‘the Λόγος,’ which is being itself, and the essence of the human and his λόγος, as two separate objects cut off from one another and placed somewhere with the purpose of examining each on its own, the way in which we bring an object of scientific research before ourselves. Moreover, the preceding should have made it increasingly clearer that everything rests upon the relation of the Λόγος, as which being itself unfolds, to the human λόγος, and vice versa. Speaking accordingly, we should not speak about a relation of the human λόγος to the Λόγος—for, indeed, the human λόγος and the Λόγος are themselves already relations. A relating is a form of harvesting and gathering—λέγειν. In Greek mathematics, the word λόγος still retains its original meaning of ‘relation.’ The relation between the human λόγος and the Λόγος is therefore not a relation between things or objects, but rather the relation between relations, i.e., pure relation without origin, and only this. However, because we are accustomed and even constantly pushed toward always thinking objects in object-like relations, a proper sojourn into the λόγος-like relation to the Λόγος is initially, and for a long time, difficult for us. More difficult still  is the proper thinking of this relation from out of it. We can never obtain this thinking, which is the only proper and true thinking, by way of various presuppositions and deductions: rather, we may only just prepare it. In the same way that the interpretation of a poem can never bring about the hearing of its poetic word by force, the interpreting of a saying and sentence of the thinker can never place us immediately into that thinking.