34 



THE GROWTH OF THE BRAIN. 



year, the difference in the final size of the animals is 

 very great. Since, then, natural death is the result of 

 old age, and old age is not attained until after growth is 

 completed, and large size depends on long-continued 

 growth, therefore long life and large size arc found 

 associated. 



The rate of growth is measured by the proportional 

 increase in a unit of time. This is well shown in the 

 accompanying curve derived from Minot's observations 

 on guinea-pigs. 1 



From the moment of birth, at least, there is a rapid 



Percent, daily increase 



8 17 



K35 120 135 150 165 160 195 



days. 



FIG. 7. Curve to indicate in growing guinea-pigs the percentage 

 of daily increase in weight, from birth to the i95th day of lite. 

 (Minot.) 



falling off in the proportional daily increase in the body- 

 weight. This is characteristic of all the higher animals, 

 man included ; so that from birth, and probably from 

 the first division of the egg, the capacity to grow is 

 undergoing an almost steady diminution. This capacity, 

 as the curve shows, must soon reach a- point where it 



1 Minot, Proc. Am. ASSOC., 1890. 



