GROWTH AND SENESCENCE 



61 



with populations of cells. The general course of growth of 

 populations and of multicellular organisms must therefore be 

 the same. As a matter of fact, it is quite a simple matter to make 

 the curves of animals, plants, and populations to coincide, at 

 least with respect to the self-inhibiting phase of growth as 

 shown in Figure 41. 



JQ Eat.9-.MosfrompjrapUon. 

 lfl , *»stJ>av5»omsw<Ung 



M 16 18 KahfcVvfeets from planting 



64 TZ BO | 88 O atJavs from planting. 



Figure 41. The growth curves of a multicellular animal (rat), population (yeast cells), 

 plant (maize and oat), and fruit (squash) were made to coincide with respect to the 

 self-inhibiting phase of growth. 



Of course, there are differences in details of the curves, as 

 shown, for example, in Figure 42 in which different species of 

 animals and man were plotted, but the general similarity be- 

 tween the curves is evident. 



Figure 42 may be of special interest to students of evolution 

 and of education on account of the fact that it shows in a most 

 striking manner the extremely long juvenile period in man. 

 Other species go through a juvenile period corresponding to that 

 in man, but the length of this period in animals is relatively in- 

 significant when compared to that of man. It may be noted in- 

 cidentally that one of the unique characteristics of the human 



