664< THE PHYSIOLOGY OF REPRODUCTION 



months is not indicated, since there are no statistical data on 

 which to found any knowledge, but from the third month 

 onwards there are a few records available. The diagram shows 

 that from the third to the fourth month the increase in growth 

 is 600 per cent., after which it quickly drops until, during the 

 last month of pregnancy, it is barely twenty per cent. 



Growth of the Body after Birth 



The rate of growth from birth to maturity has been in- 

 vestigated most fully by Minot ^ in the case of the guinea-pig. 



2 set! n 23 29 »3S 4S 



Fig. 142.— (From Minot's Problem of Age, Growth, and Death, 

 G. S. Putnam & Sons, and John Murray.) 



When this animal is born it is far advanced in development, 

 the period of gestation being unusually long. Immediately 

 after birth there is a lessening in the power of growth, a fact 

 which Minot ascribes to the physiological shock from which 

 the organism suffers as a consequence of being born. After 

 two or three days, however, the young are fully recovered, 

 and are capable of adding over five per cent, to their weight in 

 a single day. By the time they are seventeen days old they are 

 only able to add four per cent, to their weight, and by the time 

 they are twenty-four days old, less than two per cent. When 

 they have been born forty-five days, they can add only a little 



1 Minot, " Growth and Senescence," Jour, of Phys., vol. xii., 1891. " Age, 

 Growtb, and Death," Popular Science Monthly, vol. Ixxi., 1907. 



