8 THE LIFE OF SCIENCE 



sition to the new theory was considerable, but even there, and 

 bitter as it was, it did not last very long. More happy in this than 

 many other forerunners, Harvey was granted a taste of victory 

 before his death in 1657. By 1673 his cause was definitely won, 

 even in France, and the people who had been his contemporaries 

 could witness the complete supremacy of the new doctrine. 



Thus less than half a century had been needed to ensure its tri- 

 umph. The speed of this reception is less wonderful, however, 

 than the lateness of the discovery itself, for as to Harvey's priority 

 there can be no doubt. How is it then that no one anticipated him? 

 There was nothing whatever in the nature of this discovery — as 

 Harvey made it — to prevent its being made many centuries be- 

 fore: nothing but prejudice. 



Until the time of Harvey, the prevalent conception was that 

 promulgated by Galen, more than fourteen centuries earlier. It is 

 not easy at all to give a complete account of Galen's ideas, but it 

 will suffice to note the following points. According to him, the 

 blood was produced in the liver from the materials furnished by 

 our food and was then transported to the right half of the heart. 

 Some of it passed into the left half, where it was imbued with 

 new properties, and became fit to nourish the whole body. To use 

 Galenic language, the blood of the right heart was endowed with 

 "natural spirits/' that of the left heart with "vital spirits." The lat- 

 ter blood was thus essentially different from the former. They did 

 not circulate in the body, but both moved in a ceaseless ebb and 

 flow, each in its own domain. But how did the blood pass from the 

 right to the left ventricle? To explain the impossible, Galen had 

 been obliged to assume that it passed through innumerable in- 

 visible pores in the solid wall which divides the right heart from 

 the left. Nobody ever detected these pores for they are not simply 

 invisible but nonexistent. Yet Galen, supreme pontiff of Greek 

 medicine, and nine centuries later Avicenna, the infallible medical 

 pope of the middle ages, had spoken ex cathedra with such indis- 

 putable authority that this gratuitous assumption was generally 

 taken for gospel. 



