SECT. 3] AND EIGHTEENTH CENTURIES 193 



up this speculation, let us examine the growth of the chick in the 

 egg. We cannot in this case either measure its size at the moment 

 when the egg is put to incubate but it cannot be more than j^ in. 

 long, for if it were, it would be visible, and yet 25 days later it is 

 4 ins, long. Its relation is therefore as 64 to 64 millions or i to i 

 million. This growth takes place in a singular manner, it is very rapid 

 in the beginning and continually diminishes in speed. The growth 

 on the first day is from i to gi^^ and what Swammerdam calls a 

 worm grows in one day from one-twentieth or one-thirtieth of a 

 grain to seven grains, i.e. it increases its weight by 140 or 240 times. 

 On the second day the growth of the chick is from i to 5, on the third 

 day, from i to not quite 4, on the fifth day from i to something 

 less than 3. Then from the sixth to the twelfth day, the growth each 

 day is hardly from 4 to 5, and on the twenty-first day it is about 

 from 5 to 6. After the chick has hatched, it grows each day for the 

 first 40 days at an approximately constant rate, from 20 to 2 1 on each 

 day. The increase of the first twenty-four hours is therefore in relation 

 to that of the last twenty-four hours as 546I to 5 or 145 to i. Now 

 as the total increase in weight in the egg is to that of the whole 

 growth period (up to the adult) as 2 to 24 ozs., all the post-embryonic 

 growth is as i to 12, i.e. it is to the growth of one day alone early 

 in incubation as i to 7|.. . .The growth of man, like that of the 

 chick, decreases in rapidity as it advances. Let us suppose that a 

 man, at the instant of conception, weighs a hundred-thousandth of 

 a grain and that a one-month old embryo weighs 30 grains; then 

 the man will have acquired in that time more than 300,000 times 

 the weight that he had to begin with. But if a foetus of the second 

 month weighs 3 ozs. as it approximately does, he will only now have 

 acquired 48 times the weight he had at the beginning of the period. 

 This is a prodigious decrease in speed, and at the end of the ninth 

 month he will not weigh more than about 105 ozs., which is not 

 more than an average increase of 15 per month. A child three years 

 old is about half the size of an adult. If then the adult weighs 

 2250 ozs. the three-year old child only weighs 281 ozs., which is an 

 eighth of the adult weight. Now from birth to 3 years he will grow 

 from 105 to 281 or as 5 to 14, but in the following 22 years he will 

 only accumulate 2250 ozs. or eight times what he had at 3 years. 

 The growth of a man will therefore be in the first month of intra- 

 uterine life as I to 300,000, in the second as i to 48, in each of the 



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