9 6 



AGE, GROWTH, AND DEATH 



to be sure, it is going down still, but with diminished 

 rapidity. 



There is another method by which we can represent 



25811 17 a XX 45 50 



90 105 120 135 ISO 165 180 195 



FIG. 29. CURVE SHOWING THE DAILY PERCENTAGE INCREMENTS IN WEIGHT 

 OF FEMALE GUINEA-PIGS. 



this change in the rate of growth which will perhaps 

 help to illustrate it ; and in the next of our pictures 

 (Fig. 30) we see this other form of representation. 

 The first vertical line represents the length of time 

 which it takes a young male guinea-pig to add ten per 

 cent, to its weight the first time. Here the third 

 time the fourth the fifth and you see as it is 

 growing older and older it takes the animal longer 

 and longer to add ten per cent, to its weight. Finally 

 we get to the nineteenth addition, and we see that 

 the period is very long indeed. How long that 

 period is we can judge by the figures upon the left, 

 which represent the length of the periods in days. 



