THE BEGINNINGS OF LIFE. 255 



sician and biologist, William Harvey, the discoverer 

 of the circulation of the blood. The modern theory 

 of development (Epigenesis) dates from a celebrated 

 treatise by Harvey, entitled Exercitationes de Gene- 

 ratlone Animal'mm , and he also is commonly believed 

 to have taught the doctrine of the continuity of Life 

 on our globe, as opposed to views concerning its de 

 novo origination. But although, apparently, a dis- 

 believer in the doctrine that living things could take 

 origin from not-living materials (Archebiosis), Harvey 

 was a firm believer in Heterogenesis. On this subject 

 Burdach said 1 : c The rallying-cry of the adversaries 

 of spontaneous generation is the following sentence, 

 resting upon classical authority : omne vivum ex wo. 

 But they can only quote this sentence in support of 

 their opinion by neglecting the spirit and fixing merely 

 upon the letter of what was said. Valentin has 

 already called attention to the fact that Harvey him- 

 self, far from wishing to deny thereby all spontaneous 

 generation, used the word cc egg" as a general term to 

 designate a substance capable of germinating that is 

 to say, for every kind of matter which develops immedi- 

 ately into an organised body and that, consequently, 

 he extended this denomination even to the substance 

 called cc primordial mucus 2 ." 3 It seems quite certain, 

 from many passages in Harvey's writings, that he was 



de Physiologic,' 2nd edition, 1837, t. i. p. 10. 

 2 This is the name given by Burdach to the pellicle which forms on 

 organic infusions. 



