A Study of Growth 29 



Set Bi. 



After starvation the rate of growth was faster than in the nor- 

 mal animals. When Set B^ (Table II) is compared with Sets 

 A^ and A" the result is the same. This was probably due to the 

 fact that starvation had reduced the initial weight. 



IV. THEORETICAL DISCUSSION 



It has been shown that when two animals, one larger than the 

 other, are given just enough food to preserve equilibrium in the 

 large one, the smaller animal gains weight. Assuming that 

 digestion and assimilation in both cases are the same, how may the 

 facts be interpreted ? It may be safely assumed that it takes a 

 smaller amount of food to preserve equilibrium in case of the 

 small animal, than in the large one, so that the material over and 

 above that used in actual repair of the body waste goes to form 

 new tissue, to increase the size. According to this view, as the 

 small animal approaches the large one in size, which is the maxi- 

 mum weight for the amount of food taken as a basis, the rate of 

 growth should become less. It takes gradually more and more 

 material to replace waste, because of the new tissue that has been 

 continually added; hence there is less to be used in the formation 

 of new tissue. Even if more food were digested by the larger 

 individual the result would be the same. 



By feeding the large one more than enough to preserve equi- 

 librium, and the small one the same amount, the large one will 

 gain; but the rate will be slower than that of the small animal, 

 for the same reason as given above; the small one uses less for 

 repair and more goes to form new tissue. 



When animals are injured by cutting off the tails, the increase 

 in rate of growth that follows may be due either to a stimulus 

 produced by the cut, or to an increase owing to the reduction in 

 weight; that is, to a change in the relation between the body 

 material and the amount of food taken. By cutting off the tails 



