Corpse Flesh Defiles Whether Moist or Dry and the Two Acts of Awareness

From where do we know that the flesh of a corpse defiles whether moist or dry? Rabbi Shimon ben Lakish said: Scripture says "of any uncleanness of his" - to include all forms of impurity that separate from him. And Rabbi Yochanan said: "or by a bone" (Numbers 19:16) - it is comparable to a bone: just as a bone is dry, so too here even when dry. The practical difference between them is the case where the flesh has crumbled. Just as a bone was created with the body and its stock does not regenerate, so too anything created with the body whose stock does not regenerate; this excludes teeth, which were not created with the body, and excludes hair and nails, whose stock regenerates. Yet at the time they are joined to the body, all is impure. From where do we know that one is not liable until there is awareness at the beginning and awareness at the end with a lapse of forgetting in between? Scripture teaches "and it is hidden from him" twice - these are the words of Rabbi Akiva. Rabbi says: "and it is hidden from him" implies that there had been awareness, and "and he knew" - behold, two acts of awareness. Regarding the oath: One might think that one who vows to be a Nazirite or to bring an offering should bring this offering; Scripture says "or if a person swears" (Leviticus 5:4) - he is liable for the oath, not for vowing as a Nazirite or to bring an offering. One might think that one who merely meditates in the heart is liable; Scripture says "with the lips" - and not one who merely meditates. One might think I should exclude one who completes the matter in his heart; Scripture says "to pronounce."