THE STRUGGLE FOE EXISTENCE 29 



might die. Probably the boys whose stature is between 

 145 and 153 cm., and hence considerably above the normal 

 (which is between 129 and 137 cm.), are boys who have 

 outgrown their strength. On the other hand, the boys 

 whose stature is between 109 and 117 cm., and hence con- 

 siderably below the normal, are boys who have been 

 stunted perhaps because of constitutional weakness. 

 This group of extremely tall and extremely short boys 

 (for the age of lO 1 /^ years) is more likely, other things 

 being equal, to succumb to the disease, than the more 

 normal individuals; that is, outgrown strength and 

 anemic condition in the one case, and weak constitution 

 or lack of nourishment on the other, constitute conditions 

 which break down the power of resistance to disease. 

 It is therefore possible that most of the 30 cases of mor- 

 tality would be found among this group of very short 

 and very tall boys. If now, the curve were plotted for 

 the remaining 970 boys who survived, it would be found 

 that the curve was narrower than before, that is, that 

 the falling away to the right and left had disappeared. 

 In some such way as this, Nature tends to cut off the 

 extreme variates and to reduce the race or species to a 

 certain uniformity. 



The plant and animal organism is a plastic changing 

 thing. It readily adapts itself to new situations. A 

 sudden change in climate becoming a permanent con- 

 dition of a given locality will affect all forms of life in 

 that locality. Some individuals will not have sufficient 

 adaptability to adjust themselves to the nefw require- 

 ments of their surroundings; they will sicken and die. 

 Those individuals who chance to be plastic enough to 

 meet the change by new adjustments in their habits and 

 mode of life will most probably survive and pass some 



