THE EARLIEST HISTORY OF DIAPHRAGM PHYSIOLOGY

The diaphragm was recognized as a distinct anatomical structure in the earliest Creek writings. However, the precise description of wounds s uffered by warriors during the Trojan war by Homer was not tied to any particular function. The diaphragm was assimilated to the region that harbours thought. The first physiologic explanations of respiration b y Empedocles in the 5th century BC and the concepts introduced by Plat e and Hippocrates did not include a significant participation of the d iaphragm. Aristole was the first to link respiration to a particular o rgan and a specific movement of the thorax. However, he considered tha t it was the heart which caused the lungs to expand by heating them, a nd the lungs in turn forced the thorax to dilate, a concept which was to survive until the 17th century. As in Aristole's theory the diaphra gm played no role in respiration and was just a fence separating the t horax from the abdomen. A major break through occurred in Alexandria i n the 4th and 3rd century BC: Herophilus was the first to recognize th at muscles were the agents of movement and Erasistratus performed anim al experiments which showed that the respiratory muscles were the agen ts of respiratory movements, thus opening the way to the later discove ries of Galen.