Ill] OF PRENATAL GROWTH 111 



are born later than a man-child; the puppy and the kitten are born 

 easier, and in more helpless case than ours; the mouse comes into 

 the world still earher and more inchoate, so much so that even the 

 little marsupial is scarcely more embryonic and unformed*. We 

 must take account, so far as each case permits, of pre-natal or intra- 

 uterine growth, if we are to study the curve of growth in its entirety. 

 According to Hisf, the following are the mean lengths from month 

 to month of the imborn child : 



Months 01 23456789 10 



(Birth) 



Length (mm.) 7-5 40 84 162 275 352 402 443 472 490) 



500) 



Increment per — 7-5 32-5 44 78 113 77 '50 41 29 18) 

 month (mm.) 28) 



These data hnk on very well to those of Russow, which we have 

 just considered; and (though His's measurements for the pre- 

 natal months are more detailed than are those of Russow for the 

 first year of post-natal hfe) we may draw a continuous curve of 

 growth (Fig. 15) and of increments of growth (Fig. 16) for the 

 combined periods. It will be seen at once that there is a "point 

 of inflection" somewhere about the fifth month of intra-uterine life; 

 up to that date growth proceeds with a continually increasing 

 velocity. After that date, though growth is still rapid, its velocity 

 tends to fall away; the curve, while still ascending, is becoming 

 an S-shaped curve (Fig. 15). There is a shght break between our 

 two sets of statistics at the date of birth, an epoch regarding which 

 we should like to have precise and continuous information. But 

 we can see that there is undoubtedly a certain shght arrest of growth, 

 or diminution of the rate of growth, about this epoch ; the sudden 

 change of nurture has its inevitable effect, but this shght tem- 



* It is part of the story, though Ijy no mean? all, that (as Minot says) the larger 

 the litter the sooner does birth take place. That the day-old foal or fawn can keep 

 pace with their galloping dams is very remarkable; it is usually explained 

 teleologically, as a provision of Nature, on which their safety and their survival 

 depend. But the fact that they come one at a birth has at least something to do 

 with their comparative maturity. 



t Unsere Korperform und das physiologische Problem ihrer Entstehung, Leipzig, 1874. 

 On growth in weight of the human embryo, see C. M. Jackson, Amer. Journ. Anat. 

 XVII, p. 118, 1909; also J. Needham, op. cit. pp. 379-383. 



