Sextus Empiricus Pyrrhoniae Hypotyposes 1.14.126

[126] But to pass on from the subject of external admixture,—our eyes contain within themselves both membranes and liquids. Since, then, the objects of vision are not perceived apart from these, they will not be apprehended with exactness; for what we perceive is the resultant mixture, and because of this the sufferers from jaundice see everything yellow, and those with blood-shot eyes reddish like blood. ¹ And since the same sound seems of one quality in open places, of another in narrow and winding places, and different in clear air and in murky air, it is probable that we do not apprehend the sound in its real purity; for the ears have crooked and narrow passages, which are also befogged by vaporous effluvia which are said to be emitted by the regions of the head.