64 THE RATE OF GROWTH ' [ch. 



which draws us down when we would fain rise up*. For against 

 gravity we fight all our days, in every movement of our limbs, in 

 every beat of our hearts ; it is the indomitable force that defeats 

 us in the end, that lays us on our deathbed, that lowers us to the 

 grave t- 



Side by side with the curve which repiesents growth in length, 

 or stature, our diagram shows the curve of weight J. That this 

 curve is of a very different shape from the former one, is accounted 

 for in the main (though not wholly) by the fact which we have 

 already dealt with, that, whatever be the law of increment in a 

 Unear dimension, the law of increase in volume, and therefore in 

 weight, will be that these latter magnitudes tend to vary as 

 the cubes of the linear dimensions. This however does not 

 account for the change of direction, or "point of inflection" 

 which we observe in the curve of weight at about one or two 

 years old, nor for certain other differences between our two curves 

 which the scale of our diagram does not yet make clear. These 

 differences are due to the fact that the form of the child is altering 

 with growth, that other linear dimensions are varying somewhat 

 differently from length or stature, and that consequently the 

 growth in bulk or weight is following a more comphcated law. 



Our curve of growth, whether for weight or length, is a direct 

 picturs of velocity, for it represents, as a connected series, the 

 successive epochs of time at which successive weights or lengths 

 are attained. But, as we have already in part seen, a great part 

 of the interest of our curve lies in the fact that we can see from 

 it, not only that length (or some other magnitude) is changing, 

 but that the rate of change of magnitude, or rate of growth, is 

 itseK changing. We have, in short, to study the phenomenon of 

 acceleration: we have begun by studying a velocity, or rate of 



* " Lou pes, mestre de tout [Le poids, maitre de tout], mestre senso vergougnOi 

 Que te tirasso en bus de sa brutalo pougno," J. H. Fabre, Oubreto prouvenQcdo, p. 61. 



f The continuity of the phenomenon of growth, and the natural passage from 

 the phase of increase to that of decrease or decay, are admirably discussed by 

 Enriques, in " La morte," Biv. di Scienza, 1907, and in " Wachsthum und seine 

 analytische Darstellung," Biol. Ceniralbl. June, 1909. Haller (Elem. vn, p. 68) 

 recognised decrementum as a phase of growth, not less important (theoretically) 

 than incrementum: "tristis, sed copiosa, haec est materies." 



J Cf. (int. al.), Friedenthal, H., Das Wachstum des K6rpergewichtes...in 

 verschiedenen Lebensaltem, Zeit. f. allg. Physiol, ix, pp. 487-514, 1909. 



