50 Nature of the Formative Stimulus 



This would indicate then that the greater phagocytic 

 activity would be not so much the cause as rather the 

 effect of the diminution of the vital resistance of the 

 organ. And this latter would seem necessarily to be 

 due exclusively to the fact that the organ itself would 

 be at this ontogenetic stage abandoned by the particular 

 energy which had formed it, and which up till now 

 had maintained it in full vital activity, and which now 

 has not indeed ceased to exist, but has turned to other 

 regions. This transference of cellular material in process 

 of disintegration to other organs and tissues in process 

 of formation would seem in fact to demonstrate that 

 simultaneously with the diminution or the cessation of 

 the trophic stimulus in one given region there appears 

 an increase of that stimulus in another region. 



This utilization, as nutritive material, of the substance 

 of cells which are disintegrating is rendered necessary by 

 the fact that animals during their metamorphosis take 

 almost no nourishment. It follows that, if the nutritive 

 material which the abandoned parts give up to the parts 

 now more abundantly infused with trophic energy, should 

 be insufficient at the normal rapidity of disintegration, 

 the disappearance of the tissues must be accelerated. This 

 is indicated by Osborn's researches upon the influence of 

 fasting upon metamorphosis, from which it appears that 

 it is appreciably accelerated by inanition, just because of 

 the more rapid reduction and absorption of the organs 

 about to disappear. 26 



In the disappearance of the tail of the tadpole one has 

 not a senile but rather a premature involution of tissues, 



26 Osborn: Alte und neue Probleme der Phylogenese. Ergebn. 

 d. Anat. u. Entwicklungsgesch., herausg. v. Merkel u. Bonnet. Bd. 

 III. 1893. Wiesbaden, Bergmann. 1894. P. 198. 



