254 



BIOLOGY OF DEATH 



ure 64. The circles give the observed population growth, 

 obtained by census counts at 3-da.y intervals. There can 

 be no doubt that this population has grown in accordance 

 with the equation. The two final observations lie below 

 the curve, because of the diflSculty experienced, in this 



OCT 



Fia. 64. — Showing the growth of a Drosovhila population kept under controlled 

 experimental conditions. 



particular experiment, of keeping the food supply in good 

 condition after so long a period from the start. 



Let us return to the further discussion of the popu- 

 lation problem of the United States in the light of 

 the curve. 



The first question which interests one is this : When 

 did or will the population curve of this country pass the 

 point of inflection and exhibit a progressively diminishing 

 instead of increasing rate of growth? It is easily deter- 

 mined that this point occurred about April 1, 1914, on the 

 assumption that our present numerical values reliably rep- 

 resent the rate of population growth in this country. 

 In other words, so far as we may rely upon present nu- 

 merical values, the United States has already passed its 

 period of most rapid population growth, unless there 



