u8 



GROWTH 



The gradual changes in the human form and proportions 

 through the fetal and infantile stages up to the adult are shown 

 in Figure 63. Through modifications of the growth rates in the 

 various regions, the head and upper parts of the body become 

 relatively smaller, while the lower parts become correspond- 

 ingly larger. This process of a progressive differential growth, 



Z mo. (fetal) 



Newborn 



Figure 63. Changes in form and propoition of the human body during fetal and post- 

 natal life. After Stratz. 23 



spreading wavelike from head to foot, is most strikingly shown 

 in human development. The prolonged growth of the lower 

 limbs is doubtless associated with the upright posture, which has 

 been acquired by man in comparatively recent times. This pos- 

 ture requires a greater development of the lower extremities. 

 But also in all other vertebrates the general law of develop- 

 mental direction applies, to a variable degree, as will be shown 

 later. 



Some experiments by Peebles 40 are of importance in this con- 

 nection. She opened up chick eggs and made injuries with a hot 

 needle in various regions of the early embryonic disk (blasto- 

 derm). These injuries could be recognized when the embryo ap- 

 peared in later stages of development, and thus proved what 



