[The term for] a membrane covering the brain. With the so-called meningophylax ["meninx-guard"] covering the membrane, the living tissue becomes insensate and unmoving.[1] [Note] that the senses beginning from the brain proceed through the nerves up to the sensory organs. Therefore the sense of hearing proceeds as far as the base of the ears, which they call "meninges". There is a nerve provided with pores proceeding from the brain, in the pore [of which] there is an optic air-flow. There is, then, a certain air intercepted in the cavity of the ear which is combined with the meninx and the membrane. This air, then, receiving noises from the outside air and itself having an ability to conduct sound, transmits the sounds through itself into the meninx. It goes on from the rather wide passageway of the meninx. One should not consider this to be only air, even if it is of the same substance, and indivisible, as if it were always one and the same in number; rather, it is divisible into parts and generable just like any other physical component of man. It receives directly the impacts of the air outside. Therefore the ear also experiences loud sounds, when the air outside is thrust violently and with force it thrusts this similar air in the ears and often disperses it. And on account of the circumstantial functions, or the immersions in waters, this air is built in for protection of the sensory organ. Because of this nature also made the cavities of the ears spiral-shaped, so that something could not easily enter and strike the meninx.[2]