72 WITHIN AND WITHOUT 



of chemical reactions ; and we are entitled to ask 

 for an explanation of the identical behaviour of 

 the chemical reaction in connection with epiblastic 

 and mesoblastic cells both pure chemical com- 

 pounds ex hypotbesi and, as far as we can tell from 

 their normal behaviour, widely differing from one 

 another. The optic cup, or its contained fluid, is 

 one chemical compound ; epithelium is another ; 

 mesoblast is a third. We want an explanation of 

 the identical behaviour of the first with either of 

 the two latter ; and this should be borne in mind 

 that the reaction is not a mere matter of 

 " clearing " of a tissue as the histologist would 

 clear his section by oil-of-cloves or other reagent, 

 but of the construction of a different type of cell 

 epithelial, not connective tissue. 



It certainly follows that there must be some 

 superior, at least widely different, agency at work 

 than one of a purely chemical character some- 

 thing which transcends chemical operations. 

 This is precisely what the Vitalist claims. No one 

 will fail to award praise to any attempts to explain 

 the phenomena of Nature, whether within or 

 without any system. Loeb s book sets out to do 

 a great deal more to explain what it does not 

 explain the Organism as a Whole, and thus to 

 give a philosophical explanation of man. It even 

 claims to afford hints for a rule for his life, at least 

 so we gather from the Preface, where, alluding to 

 " that group of freethinkers, including d'Alembert, 

 Diderot, Holbach and Voltaire," the author tells 

 us that they " first dared to follow the conse- 

 quences of a mechanistic science incomplete as 



