SECT. 2] 



AND WEIGHT 



423 



of inflection, and k a third genetic growth-constant, the fractional 

 decHne in the velocity of growth), it was possible to plot growth- 

 curves for all animals to the same base, and so to determine their 

 age-equivalence. Thus they found that i rat month was equivalent 

 to ii-gi cow months, and i guinea-pig gram to 509-1 cow grams. 

 They finally constructed a table (Fig. 51), in which the value of ^ 

 was given for a great many animals, and a logarithmic graph, from 



001 



.02 



Value of k. 



.03 .M .05 06 -07 .C8 -09.1 Z 



5 .6 7 .8 .9 10 



CotVC. 

 Mos; 



Fig. 51- 



which can be read off the time in months (conception age) at which 

 the animal with the constant k in question will arrive at 10, 20, 30 

 or 90 per cent, of its mature weight. 



Brody next considered the growth-constants during the autokinetic 

 or self-accelerating phase of growth. He subjected the methods 

 which had previously been used to represent growth to severe 

 criticism, part of which has already been referred to. Thus, in the 

 case of Minot's method, increments of growth are regarded as 

 being added on discontinuously at the terminal points of arbitrary 

 time periods, whereas growth is really a continuous process, and 



