Ill] OF GROWTH IN INFANCY 113 



porary set-back is immediately followed by a secondary, and equally 

 transitory, acceleration *. 



Mean weight in grams of American infants during ten days 

 after birth. (From Meredith and Brown) 



Weight 



The set-back after birth of which we have just spoken is better 

 shewn by the child's weight than by any linear measurement. During 

 its first three days the infant loses weight visibly, and it is more than 

 ten days old before it has made up the weight it lost in those first 

 three (Fig. 17). 



It is worth our while to illustrate on a larger scale His's careful 

 data for the ten months of pre-natal life (Fig. 18). They give an 

 S-shaped curve, beautifully regular, and nearly symmetrical on 

 either side of its point of inflection; and its differential, or curve 

 of monthly increments, is a bell-shaped curve which indicates with 

 the utmost simplicity a rise from a minimal to a maximal rate, and 

 a fall to a minimum again. It has a close family Hkeness to the 

 well-known "curve of probabihty," of which we shall presently 

 have much more to say; it is a curve for which we might well 

 hope to find a simple mathematical expression f- 



These two curves, then, look more "mathematical," and less 

 merely descriptive, than any others we have yet drawn, and much 



* See especially, H. V. Meredith and A. W. Brown, Growth in body-weight 

 during first ten days of postnatal life, Human Biology, xi, pp. 24-77, 1939. Also 

 {int. al.) T. Brailsford Robertson, Pre- and post-natal growth, etc., Amer. Journ. 

 Physiol. XXXVII, pp. 1^2, 74-85, 1915. 



t The same is not less true of Friedenthal's more elaborate measurements, in his 

 Physiologie des Menschenwachstums, 1914; cf. Needham, op. cit. p. 1677. 



