as for the eyelashes of the upper eyelid if they were curved upwards they would block what descends to the eye there and if they were extended downwards they would harm the sight which is why they were created erect and forward. were it not for the hardness of the place where these eyelashes are inserted in the eyelids they would be as in the hair relaxed. that is why their place of insertion was made in the cartilaginous mass that we mentioned. then this mass was made perforated because if it were solid the excess fluid that occurs between the two strands would be trapped between them and harm the eyelid. that is why that mass was created perforated and that is why eyelashes and the like come out from the edge of the eyelid. because of the hardness and dryness of the place where the eyelashes are inserted very little moisture penetrates the hair which is why all hair turns gray with age except for these eyelashes because their whiteness is very harmful to the sight. and allah is the grantor of success.
وأما هدب الجفن الأعلى فإنها لو كانت منعطفة إلى فوق لحبست ما ينزل إلى العين عندها، ولو كانت مسترسلة إلى أسفل لأضرت بالإبصار فلذلك خلقت منتصبة إلى قدام، ولولا صلابة مغرس هذه الأهداب في الجفنين لكانت تكون كما في الشعور مسترخية ولذلك جعل مغرسها في الجرم الغضروفي الذي ذكرناه ثم جعل هذا الجرم منثقبا لأنه لو كان مصمتا لكان ما يحصل من الفضول بين الطاقين يحتبس بينهما ويضر بالجفن، فلذلك خلق ذلك الجرم منثقبا ولذلك يخرج من طرف الجفن الرمص ونحوه. ولأجل صلابة مغرس الأهداب ويبوسته قل جدا ما ينفذ في الشعر من الرطوبة فلذلك جميع الشعور تشيب في الكبر إلا هذه الأهداب لأن بياضها شديد الإضرار بالبصر. والله ولي التوفيق.