THE STRUGGLE FOR EXISTENCE 29 



might die. Probably tlic boys wlioso stature is between 

 145 and 153 cm., and hence consid('ia))ly above the iioniial 

 (which is ])etween 129 and l.'!7 ciii.), are boys wlio have 

 outgrown tlieii- strengtli. On llic other band, the boys 

 wliose statui'e is between 10!) ;ind 1 17 <'ni., ;md 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 IQi^ years) is more likely, other things 

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

 normal individuals; tliat 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 80 cases of mor- 

 tality would be found among this grou]i 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 cilrve 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 unif on n i t y . 



The plant and animal organism is a. plastic, changing 

 thing. It readily adapts itself to new situations. A 

 sudden eliange 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 

 adflptability to adjust themselves to the new require- 

 ments of their surrouiulings; tliey 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 



