Pesachim, Chapter Two, Mishnah 7:
The Mishnah opens: "Ein shorin es hamursan letarnegolim" - one may not soak bran, which is the coarse husks of the grain, in order to feed it to chickens. Even though bran is not the main part of the grain, it is liable to become chametz while soaking, and therefore soaking it is forbidden.
"Aval chotlin" - one may place the bran into very hot water, boiling water, since the extreme heat prevents it from becoming chametz.
Another use for bran - in the bathhouse:
"Ha'ishah lo tishreh es hamursan shetolich beyadah lamerchatz" - a woman may not soak bran in order to carry it in her hand to the bathhouse. Apparently it was used as a kind of cleaning agent, rubbed onto the skin, and here too the concern is that it may become chametz.
"Aval safah hi bapesoles yavesh" - she may rub the bran on her skin while it is dry. The bran is dry, and even if her skin itself is moist, it is permitted. Some explain that the moisture on her skin must be perspiration alone, but water that she washed herself with, according to those explanations, is problematic.
Medicinal use of wheat kernels:
"Lo yalus adam chittin veyaniach al makaso baPesach, mipnei shehen machmitzos" - a person may not chew wheat kernels and place them on his wound. Apparently this was an accepted medical practice, but the saliva that mixes with the kernels of grain brings them to a state of chametz, and therefore they may not be used as a bandage or as a remedy of any kind.
In summary: This Mishnah deals with the concern of leavening in uses that are not for human consumption: soaking bran as feed for chickens is forbidden, while scalding it in boiling water is permitted; carrying soaked bran to the bathhouse is forbidden, while rubbing with dry bran is permitted; and chewing wheat and placing it on a wound is forbidden, because it becomes chametz.