APPENDICES 



APPENDIX I 



GREAT EVENTS IN BIOLOGY 



The foundation-stones of the science were laid by Aristotle (384- 

 322 B.C.), who began to classify and dissect, who understood what 

 is meant by homology and by correlation, who saw the beating 

 heart in the developing chick-embryo, and had a glimpse of the deep 

 uniformity of development in all animals. But perhaps his greatest 

 contribution, long of being generally imitated, was his insistence 

 on observation as antecedent to reflection. Yet centuries passed 

 before he found an outstanding successor in Galen (a.d. 131-201), 

 who dissected much, and may be called the first experimental 

 physiologist. In spite of an occasional irrepressible observer, the 

 letter of Aristotle was persistently stronger than his spirit, as far as 

 biology was concerned; and it was not till the sixteenth century that 

 the fetters were broken. The Belgian anatomist, Andreas \^esalius 

 (1514-64), has been well called "the emancipator of biology from 

 the traditions of the ancients", for he insisted on an independent 

 scrutiny of facts. Another even greater initiator was William Harvey 

 (1578-1657), whose De Motu Cordis et Sanguinis was published in 

 1628. It was not merely that he demonstrated what his precursors 

 and anticipators (like Servetus and others) had hinted at, the circu- 

 lation of the blood; his larger importance was in showing how the 

 flow was sustained. This was also the epoch-making first proof that 

 some processes in the living body may be in some measure inter- 

 preted in terms of mechanics. It was the first instance of a "legiti- 

 mate materialism" in biology. Moreover, although the axiom 

 "omne vivum ex ovo" was not Harvey's, he had a prescient con- 

 viction that "all animals are in some sort produced from eggs", 

 and laid another foundation-stone in declaring that practically 

 every organism begins its individual life from an apparently simple 

 primordium in which "no part of the future organism exists de 

 facto, but all parts inhere in potentia". And yet, as Huxley points 

 out, Harvey believed in spontaneous generation as firmly as 

 Aristotle did. It seems fair to rank the Italian Redi (1626-98) as a 

 foundation-layer, since he was foremost in proving experimentally 

 that spontaneous generation did not occur in the cases where this 

 had been alleged. But the heresy of abiogenesis has died hard. 

 Even Pasteur and Tyndall hardly gave it its death-blow. 



Another fundamental step is associated with the invention of the 

 compound microscope, shared in by Galileo, about 1610, for this in 



VOL. II zz 



