igo SCIENCE AND THE HUMAN MIND 



specific character has been shown to contain some 

 record of the much more general and infinitely more 

 prolonged development of the whole species. 



Harvey had put the science of observational em- 

 bryology on a correct basis in his De Generatione 

 Animalium in 1651, but the true founder of the 

 modern development was Caspar Frederick Wolff (1733- 

 1794), who was born in Berlin, and died at St Peters- 

 burg, whither he had been summoned by the Empress 

 Catherine and where he had long occupied a professor- 

 ship. Wolff's work was neglected and discredited 

 during his lifetime, but in truth he foreshadowed all 

 the modern theories of structure. He made a study 

 of cells, by means of the microscope, and showed the 

 progressive formation and differentiation of the various 

 organs in a germ originally homogeneous in character, 

 thus destroying the previous belief that every organ 

 made a separate and distinct start. 



It is now known that the multiplication and differen- 

 tiation of cells is a process common to all embryonic 

 development, and that organic growth proceeds on 

 identical lines throughout the whole animal creation. 

 It becomes probable that the development of the higher 

 animals repeats, within certain limits, the different 

 stages of the process gone through by creatures who 

 are lower in the scale of existence. It remained only 

 for Von Baer, about 1820, to show that the pre-natal 

 growth of man took place on lines identical with those of 

 all other animals, and thus to forge one link in the chain 

 of evidence which binds man to the rest of creation. 

 It is perhaps difficult for the untrained mind to 

 appreciate fully the value we must attach to such 

 discoveries, which provide the most convincing and 



