Ko. 641] 



THE RATE OF GROWTH 



553 



The rate of growth of an animal recovering from an 

 initial period of suppression may be studied in compar- 

 ison with that of a rat on adequate diet. Take the case 

 of rat No. 1012 (male). The computed values of dx/dt 

 have been plotted in Fig. 6. The time at which dx/dt 

 was a maximum in the first cycle was made to coincide 

 with the maximum for the first cycle of the rats on ad- 

 equate diet. This arrangement was adopted to facilitate 

 comparison. 



The curve for the first cycle as plotted in Fig. 6 is a 

 very fair duplicate of the curve for the same cycle of 

 growth for the rats on adequate diets. There is more 

 difference in the case of the second cycle. The curve for 

 rat No. 1012 has a maximum which is lower and occurs 

 somewhat nearer the dx/dt axis than that of the other 

 class of animals. In other words, the increased weight 

 due to formation of fat in this animal began relatively 

 earlier than in animals on adequate diets. In the main, 

 however, there are no striking differences between the 

 relative growth rates in the two cases, except that their 

 maxima are nearer together. 



The same sort of computations have been made for the 

 growth of female rats and they are showTi graphically in 

 Fig. 7. An extended discussion of them is unnecessary, 

 as it would be in many respects a mere repetition of what 

 has been said. A comparison of the curves of female rats 

 on adequate diet with those of rat No. 2033 shows {a) 

 that the rate of resumed growth w^as faster in the second 

 cycle, {h) that the second cycle was of shorter duration, 

 and (c) that the maximum of the second cycle lay clo.-^er 

 to that of the first cycle than in the case of rats on ad- 

 equate diet. 



In view of the fact that rats recovering from initial 

 suppression reach mature weight more quickly than an- 

 imals fed on adequate diets, it is somewhat surprising to 

 find such a close similarity in the v.iliics of dx/dt for the 

 same time intervals. One might expect that the curves 

 for the recovering animals should be higher and steeper. 



