Alexandria


Alexandria
   The Alexandrian physicians were the first in medical tradition to perform systematic dissections of human cadavers. Among the main contributions in the field of human anatomical dissections, those made by Herophilus of Chalcedon( 335- 280 B.C.E. ) stand out.

    Herophilus' contribution to brain anatomy was priceless. He was proclaimed as '' father of anatomy''. He was the first to appreciate the true nature of the nerves as the communications network of the body. Firstly, he regarded the brain as encephalon and also the suggested the cerebellum as parencephalon. Secondly, he made significant discoveries of the nervous system. One of them was the distinction between the cerebrum and the cerebellum and their different functions. Moreover, he found the difference between nerves and arteries.In addition, he regarded the brain as the seat of intellect as well as the centre of nerves. Not only he studied the internal surface of the skull, but also he found and described cranial nerves, such as optic, oculomotor, trigeminal, facial, auditory and hypoglossal.He also described the main ventricles of the brain ,making the fourth ventricle the seat of intellect. He described the floor of the fourth ventricle , comparing the indentation in the brainstem to the cavity in the ink pen used by the scholars in Alexandria, so we still have the term '' calamus scriptorius'' ( calamus> κάλαμος - the object made by pen) . We also have the term '' torcular herophili'' , which he identified as the confluence of the cerebral veins. Herophilus called the three membranes of the brain '' chorioid'' , because they resembled the chorionic envelope surrounding the fetus. Specifically, the lateral ventricle was  responsible for judgement and was located in the anterior part of the brain, Third ventricle was found in the middle part and regulated cognition. However, the fourth ventricle, which was in the posterior part was regarded as the most important. Herophilus placed the central control in the fourth ventricle of the brain. For him this ventricle was the seat of hegemonikon. As Galen reported : '' Herophilus placed the controller, hegemonikon, in the hollow of the brain which is also the base.
In general, Herophilus recognized that ventricles allow passage of the psychic pneuma, because they are in reciprocal communication. Therefore, there is an obligatory passage from the front ventricle of the cerebellum.
    His most impressive achievement in neuroanatomy was the identification of the peripheral and cranial nerves that connect to the brain so a to allow motion and sensation. He was the first who observed the difference between motor and sensory nerves. His realization was that motor nerves (= kinetika)  joined to muscle and sensory nerves (= aisthetika) to organs of sensation.
    Finally , he described lower brainstem and spinal cord as one structure called as '' spinal marrow''. Herophilus found that all the nerves of the body below the head grow either from cerebellum or from the spinal marrow.





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