There are [stringencies] that apply to white hair which do not apply to expansion, and there are [stringencies] that apply to expansion which do not apply to white hair: White hair renders tumah initially, renders tamei with any shade of white, and has no symptom whereby it is tahor. There are [stringencies] that apply to expansion: Expansion renders tamei with any amount, renders all negaim tamei, [and renders tamei when it spread] outside the nega, which is not the case with white hairs.

There are [stringencies] that apply to living skin which do not apply to expansion, and there are [stringencies] that apply to expansion which do not apply to living skin: Living skin renders tamei initially, and renders tamei with any appearance. There are [stringencies] that apply to expansion: Expansion renders tamei with any amount, renders all negaim tamei, [and renders tamei] outside the nega, which is not the case with living skin.