PHASES IN THE LIFE OF THE INDIVIDUAL 669 



five years of age ; girls at twenty or twenty-one. In both sexes 

 the weight of the body tends to increase until about the fiftieth 

 year or somewhat later, owing to an accumulation of fat, but 

 there are of course very many exceptions. 1 



That good nourishment and a healthy environment favour 

 growth is a fact recognised by all. So also systematic exercise 

 has been found to increase both the weight and the height, 2 and 

 it has been shown further that well - developed children are 

 more efficient mentally and take better places at school than 

 ill-developed and badly-nourished ones. 3 



Percentage. Jncwnwnti CAicb 



03J8I3I8KJ83JM46 56 66 90 106 



FIG. 147. (From Minot's Problem of Age, Growth, and Death, 

 G. S. Putnam & Sons, and John Murray.) 



In horses and other domestic animals the effects of feeding 

 on growth and general development are remarkable. Thus it 

 is said that a highly-fed thoroughbred at two years old is 

 " furnished " and looks as old as an ordinary horse at four 

 years old. 4 



1 See Minot, Popular Science Monthly, vol. Ixxi., 11)07. Minot states 

 that his calculations are based on data supplied by Professor Donaldson. 

 See also Lee, Article "Reproduction," in Howell's American Text-Book of 

 Physiology, 2nd Edition, London, 1900. 



2 Beyer, "The Influence of Exercise upon Growth," Jour, of Exper. 

 Medicine, vol. i., 1896. 



3 Porter, "The Physical Basis of Precocity and Dulness," Trans. Acad. 

 of Science, St. Louis, vol. vi., 1893. 



* Smith, loc. cit. 



