RENAISSANCE 109 



chamber, from which "soot" was given off through the pulmonary arteries; 

 the wall between the right and the left ventricles was full of fine pores, 

 through which the blood oozed from the right to the left side, to be ' 'cleansed" 

 by the action of the pneuma. Galen had but vague ideas as to the movement 

 of the blood in the vessels; in the veins, at any rate, the blood moved, accord- 

 ing to his notion, alternately in both directions. Such was Galen's theory 

 of the blood-vessels and their contents, and in this form it was still accepted 

 by the great anatomists of the sixteenth century. All its vagueness and many 

 contradictions would undoubtedly have been realized long before had not the 

 blood-vessel system of old been considered the very centre of life itself; 

 the mysterious pneuma was only one side of this blood's specific life-content; 

 the different kinds of soul that man was believed to possess — the "vegeta- 

 tive," with the liver as its organ, and the "animal" in the heart — were 

 also intimately connected with the blood and through it affected the entire 

 body.^ Speculation about these components in the organism certainly did not 

 make the conception of the vascular system any clearer; moreover, it en- 

 tailed the risk that any critical discussion of these organs might be inter- 

 preted as an attempt to call into question the immortal soul of man, which 

 would inevitably have involved the scientific student in trouble with the 

 theologians and the Inquisition. Typical in this respect is Vesalius's attitude 

 regarding the pores in the dividing wall between the right and the left 

 heart-chambers; he could not find any trace of them, but cautiously adds 

 that all the same the blood might perhaps be able to ooze through the wall 

 itself. His pupils adopted the same cautious attitude on this point, particu- 

 larly Fabrizio, the discoverer of the venous valves. 



To attack the traditional theory of the blood-vessels was thus a task 

 that required courage. The man who was the first to grapple with an at- 

 tempt to reform one detail of the old theory was in fact well qualified in that 

 respect, a man whose whole life had been spent in a struggle against time- 

 honoured ideas and who was at last to die for his principles. This was the 

 well-known religious enthusiast and martyr, Michael Servetus. 



Miguel Servet y Reves, which was his real name, was born at Vil- 

 lanueva in north Spain, of noble parents. The date of his birth is not known 

 for certain (1509 or 1511); how he spent his youth is also unknown. It was 

 apparently at an early age, however, that he experienced that restlessness of 

 spirit which throughout his life made it impossible for him to settle to any- 

 thing permanent or find any definite mission in life. He became one of those 

 passionate, revolutionary, and at the same time deeply mystical enthusiasts 

 who were particularly in evidence during the Renaissance. Having visited 



' The theory that the soul, not only of man, but also of animals, is in the blood occurs 

 in the Old Testament: "Only be sure that thou eat not the blood: for the blood is the life; and 

 '■hou mayest not eat the life with the flesh" (Deuteronomy xii. 2.3). 



