Prenatal Growth of the Human Body. 127 



Although the growth rate at the end of the fetal period ia far less 

 than at the beginning, it is still very rapid as compared with the 

 growth rate after birth. If the relative monthly growth rate of the 

 last fetal month (.45) were maintained during the first year after 

 birth, the weight of the body at the end of the first year would be 

 over 250 kilograms! This marked diminution in the growth rate 

 after birth indicates that the prenatal conditions are far more favor- 

 able to growth than the postnatal. 



As may be seen by the" dots in Fig. 1, the volume in cc. of the fetal 

 specimens studied, the age being estimated from their length, coi*- 

 responds) roughly to the curves of growth in weight, where the age 

 was determined from menstrual history. We should expect the curve 

 of growth in volume to differ slightly from that of weight, on account 

 of slight changes in the specific gravity of the fetus. In the earlier 

 months, the specific gravity of the embryo is very little over 1, though 

 in later fetuses it reaches 1.04 or 1.05. 



2. Relative Growth of the Principal Parts of the Body. 



Since growth is not uniform in the various parts of the body, these 

 must be separately considered. No data have been published showing 

 the relative size of the head, trunk and extremities in the various 

 prenatal months, although it is well known that the head is at first 

 relatively large and the extremities small. My own observations on 

 the relative growth of the various* parts in 32 specimens are included 

 in Table IV. The relative size of the head was also observed in 5 of 

 the His models (Table II). 



The growth of the various parts in the specimens observed is illus- 

 trated graphically by the curves of relative growth shown in Fig. 2.^ 



The unbroken lines connect points corresponding to the observations 

 on the 32 specimens in Table IV. The dotted line at the beginning 

 of the "Head" curve indicates approximately the relations found 

 in the His models representing embryos in the latter part of the 1st 



"It must be borne in mind that the curves of relative growth merely 

 indicate whether the part is growing more or less rapidly than the average 

 rate of the body as a whole, whose absolute growth curve is shown in 

 Fig. 1. 



