GREEK BIOLOGY AND MEDICINE brain, and the distinctions between vessels and nerves, and divided the motor from the sensory nerves, — an immortal achievement. His autopsies extended the knowledge of patho- logical conditions of the internal organs. Mechanical views prevailed in his physi- ology, in which Nature's horror vacui played a leading role. For him, the body, com- pounded of atoms, was vivified by warmth from without: his physiology felt the need of some explanatory principle like oxygen. The source of organic energy was two-fold, the blood propelled through the veins, and the pneuma " which is the energy carrier and dom- inates all vital phenomena. Renovation of the pneuma is brought about through respira- tion, whereby air penetrates into the left side of the heart through the pulmonary vein. Thus two varieties of pneuma result, of which one (the vital pneuma) is propelled into the arteries, its function being to regulate vegeta- tive processes throughout the body; whilst the other (soul-pneuma) has the brain as its goal, whence it effects movement and sensation by way of the nervous system " (Neuburger, p. 182). One sees that Erasistratus was kept from recognizing the circulation of the blood
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