the answer as for the first if the marrow were to be placed from the inside it would become very hot due to its proximity to the heart and that would take it out of the temperament it needs for the power of sensation and voluntary movement to penetrate it and for it to be a representative of the brain in conveying these powers to the nerves and their penetration into it to the other organs. therefore it was necessary to place the marrow from behind so that it would be further from being very hot due to the heat of the heart. however three bones were placed behind it and it was covered from contact with harmful things so both purposes were achieved which are the marrow being far from the heart while being covered by the bones and being protected by them from harmful things.
الجواب أما الأول فلأن النخاع لو جعل من داخل لكان يتسخن جدا بقربه من القلب، وذلك يخرجه عن المزاج الذي يحتاج إليه في أن تنفذ فيه قوة الحس والحركة الإرادية وأن يكون نائبا عن الدماغ في إيصال هذه القوى إلى الأعصاب ونفوذها فيه إلى الأعضاء الأخر فلذلك احتيج أن يجعل النخاع من خلف ليكون أبعد عن التسخين الشديد بحرارة القلب، ومع ذلك جعل من ورائه عظام ثلاثة وتستره عن ملاقاة المؤذيات فحصل بذلك الغرضان جميعا وهما بعد النخاع عن القلب مع انستاره بالعظام وانحراسته بها عن المؤذيات.