The Greek physician Galen believed that muscles contracted due to a fluid flowing into them, and for 1500 years afterward, it was believed that nerves were hollow and that they carried fluid.
كان الطبيب اليوناني جالينوس يعتقد أن العضلات تتقلص بسبب تدفق السوائل عليها، بعد 1500 سنة، كان يُعتَقَد أن الأعصاب جوفاء وتحمل السوائل.