Ill] OF PRE-NATAL AND POST-NATAL GROWTH 77 



method of nutrition has its inevitable effect; but this shght 

 temporary set-back is immediately followed by a secondary, and 

 temporary, acceleration. 



It is worth our while to draw a separate curve to illustrate on 

 a larger scale His's careful data for the ten months of pre-natal 

 life (Fig. 9). We see that this curve of growth is a beautifully 

 regular one, and is nearly symmetrical on either side of that point 

 of inflection of which we have already spoken; it is a curve for 

 which we might well hope to find a simple mathematical expression. 

 The acceleration-curve shown in Fig. 9 together with the pre-natal 



20 22 24 26 28 30 

 days 



Fig. 10. Curve of growth of bamboo (from Ostwald, after Kraus). 



I 



curve of growth, is not taken directly from His's recorded data, 



but is derived from the tangents drawn to a smoothed curve, 

 corresponding as nearly as possible to the actual curve of growth : 

 the rise to a maximal velocity about the fifth month and the 

 subsequent gradual fall are now demonstrated even more clearly 

 than before. In Fig. 10, which is a curve of growth of the 

 bamboo*, we see (so far as it goes) the same essential features, 



* G. Kraus (after Wallich-Martius), Ann. du Jardin hot. dc Buitenzonj, xii, 1, 

 1894, p. 210. Cf. W. Ostwald, Zeitliche Eiyenschaften, etc. p. 56. 



