90 AGE, GROWTH, AND DEATH 



quire such extraordinary amounts of food as the 

 large animals, should we experiment with them. Ac- 

 cordingly with guinea-pigs I began making, years 

 ago, a long series of records, taking from day to day, 

 later from week to week, and then, as the animals 

 grew older, month by month, the weight of recorded 

 individuals. There was thus obtained a body of 

 statistics which rendered it possible to form some 

 idea of the rapidity of growth of this species of 

 mammal. 



Now in regard to the rapidity of growth, it is en- 

 cessary that we form clearer notions than perhaps you 

 started out with when you came into the hall this 

 evening. I will ask for the next of our pictures on 

 the screen, where we shall see illustrated to us older 

 methods of recording the progressive growth of 

 animals. Fig. 27 is a chart taken from the records 

 of my friend, Dr. Henry P. Bowditch, showing the 

 growth of school children in Boston. Here we have, 

 in the lower part of the figure, the two curves of 

 growth in weight. The upper curve is the weight of 

 boys. We can follow it back through the succession 

 of years down to the age of five and one half years, 

 when the records begin. The child weighs, as you 

 see, a little under forty pounds at that time. When 

 the boy reaches the age of eighteen and one half 

 years, he approaches the adult size, and weighs well 

 over 130 pounds. Here then we see growth repre- 

 sented to us in the old way, the progressive increase 

 of the animal as it goes along through the succession 



