12 GENERAL PHYSIOLOGY 



withstanding the fact that here and there an isolated physiological 

 observation was made. This condition of stagnation continued 

 until into the sixteenth century. 



C. THE PERIOD OF HARVEY 



An independent advance in physiology is first met with in the 

 sixteenth century. One of the first to abandon Galen's system 

 was Paracelsus (1493-1541), who developed a complete system of 

 nature. It was permeated with theosophical notions, a tendency 

 that appeared still stronger in his followers and drove them wholly 

 over to mysticism. Nevertheless, it contained many original, 

 although frequently absurd, ideas. Paracelsus opposed the weak 

 echoes of Galen's system and its outgrowths which had appeared 

 during the middle ages, and this was at that time an important 

 advance. The foundation of his system is the unity of nature. 

 Nature is a unit, the macrocosm. In man as the centre of nature 

 all forms of existence are contained. Hence, man is to be regarded 

 as a microcosm. Nature, however, must not be considered as com- 

 plete but as for ever becoming. The more special aspects of his 

 system are arbitrary and unimportant, and, as is usual in such 

 cases, this first beginning of independent investigation was com- 

 paratively crude ; before all other things it lacked a purely empirical 

 and experimental basis. 



At the same time, in France and in Italy a freer tendency began 

 to appear in the medical schools. Fernelius (1497-1558) had 

 many new ideas, although they were based wholly upon Galen's 

 system. From the various forms of Galen's pneuma he separated 

 the anima. The former consists of the most subtile material 

 .substance ; the latter is the soul, which is to be recognised only 

 by its effects. He advanced the further idea that the pheno- 

 mena within the organism depend finally upon certain mysterious 

 causes. 



Special physiological investigation received an impulse from the 

 great anatomical discoveries in the schools of France and Italy, 

 where knowledge of the anatomy of the human body was placed 

 upon a wholly new and strictly empirical basis by Vesalius, 

 Eustachio, Faloppio, arid others. Researches upon the structure 

 of the heart and the course of the vessels were the most fruitful for 

 physiology. The doctrine of the circulation of the blood, as 

 founded by Galen, underwent fundamental changes. By proving 

 the imperviousness of the interventricular septum, Serveto 

 (1511-1553) refuted Galen's idea that the blood goes from the 

 right ventricle of the heart directly into the left ventricle. His 

 followers, Colombo (d. 1559) and Cesalpino (1519-1603), added to 

 this new facts upon the circulation of the blood in the lungs ; and 

 Argentieri (1513-1572), who opposed the doctrine of the animal 



