324 



SERGIUS MORGULIS 



The curves of posterior regeneration obtained for Podarke and 

 for the tadpoles of Rana clamitans present a striking paralleUsm 

 to the curves of growth of various animals worked out by Minot 

 ('07), and to this paralellism I wish now to direct attention. 

 Minot's curve is constructed upon the principle that the growth 

 for each successive period may be expressed as a fraction of the 

 amount of growth for all preceding periods; i.e., the size at the 

 beginning of the period under consideration; it always shows a 

 rapid rise at first, then falls abruptly, and later continues to slope 



25 



Days sincS operation 



Fig. 2 Curve showing the rate of regeneration of the tail of tadpoles of Rana 

 clamitans Lat., as expressed in the daily increase in length during thirty-eight 

 days following operation. Copied from Durbin ('09, p. 409, fig. 3) The Journal of 

 Experimental Zoology. 



down gradually, reaching practically the zero point. If we 

 examine any of the curves of growth given by Minot, for instance, 

 fig. 21 on page 197, reproduced below, it will, be seen that the 

 power of growth, very slight at first, gathers great strength two 

 or three days after birth. Rapid growth lasts only a few days, then 

 the rate decreases, at first, with notable rapidity, but after 

 forty-five days only very slowly. 



It is unnecessary to dwell at length upon this parallelism be- 

 tween the curves of the rate of regeneration and those of the rate 

 of normal (formative) growth, which is made evident by a com- 

 parison of figs. 1, 2, and 3. The curves are all of fundamen- 

 tally the same form. The rapid fall in the curves succeeding the 



