286 



INTRODUCTION 



[Ch. X 



few hours, a period of rapid growth due almost exclusively to 

 imbibed water, during which the percentage of water rises 

 from 56 to 96 ; lastly comes the period of histological differen- 

 tiation and deposition of formed substance, during which the 

 amount of dry substance increases enormously, so that the per- 

 centage of water falls to 88 and below. But the growth is due 

 chiefly to imbibed water. 



The foregoing facts thus unite in sustaining the conclusion 

 that at the period of most rapid growth of organisms growth 

 is effected by water more than by assimilation. 



In later development the proportion of water slowly falls. 

 This fact is well brought out in the following tables : — 



TABLE XXIII 



Showing the Peeoentase of Water in Chick Embryos at Various Stages 

 UP to Hatching, prom Potts, '79 



TABLE XXIV 



Showing thj; Percentage of Water in the Human Embryo at Various 

 Stages up to Birth, from Fehling, '77 



