SECT. 2] AND WEIGHT 413 



last part of the curve, data on the weight of new-born infants, born 

 at different times, some earHer and some later than the normal. We 

 have, moreover, already seen that the curve constructed by Vignes 

 for human embryonic growth shows an S-shaped conformation. 



In 1926 Robertson published a long paper in which he reviewed 

 the work which he and his collaborators had done on the subject 

 of the autocatalytic theory of growth. Here he showed that the fall 

 in the relative value of the velocity constant of (asymmetric) auto- 

 catalysis during the embryonic growth of the mouse followed almost 

 exactly the same curve as the fall in the chemical nucleoplasmatic 

 ratio as determined by LeBreton & Schaeffer (see Section 10-2). It is 

 not clear, however, what significance is to be attached to this finding, 

 especially as Crozier and Brown have shown that at least two velocity 

 constants must be postulated in a given cycle. Robertson himself 

 drew no theoretical conclusion from it. 



Robertson regards the several growth-cycles distinguishable in the 

 life of an animal as being independent, in that they each have a 

 different catalyst. The first of these in the case of the mouse has an 

 equation of the type 



where x is the growth attained at time /, A the maximum growth 

 attainable in the cycle under consideration, t the time required to 

 attain half the maximum growth and k a specific velocity constant. 

 B is another specific constant, an index of the asymmetry of the curve. 

 The second and third cycles have the formula 



log-^-^ = A(^-0, 



where the symbols are as before. He considers that skewness or 

 asymmetry originates probably in a progressive diminution of the 

 velocity constant as described above. 



Robertson's suggestions were not allowed to go uncriticised. 

 Meyer, in his report of data for the growth of the human foetus, took 

 occasion to attack both them and the traditional Minot standpoint. 

 On the whole, Robertson's autocatalysis theory emerged with less 

 damage than Minot's cytomorphosis theory. Meyer brought into the 

 light what had been one of the most disturbing features of the Minot 

 method, namely, the absurd values which the percentage growth- 



