 his saying the brain is divided into a veiled substance. by the brain here he means what is below the skull because if he meant the head itself the skin the periosteum and the skull would be included in it.
قوله الدماغ ينقسم إلى جوهر حجابي يريد بالدماغ ها هنا مادون القحف إذ لو أراد الرأس نفسه لدخل فيه الجلد والسمحاق والقحف.