VI 



GROWTH OF MAMMALS 



221 



300r 



6 200- 



100 



[300 



200 



100 







100 



400 



weight 



200 300 



Time in days 



Fig. 26. Growth of the albino rat ((5). Donaldson's data. Length growth 

 growth — — — . Calculation according to equations (5.28, 5.29) shows two growth 

 cycles with a shift of the values of the constants at approximately 100 g body weight. 



After Bertalanffy, 1941b. 



tropic or other hormones of the hypophysis. This is indicated by the fact that hypophysec- 

 tomy, i.e. removal of the whole organ, entails more drastic changes of metabolism than the 

 dwarf gene of mice which causes lack of the eosinophilic cells and presumably of somato- 

 tropin. The deficiency in growth hormone in dwarf mice inhibits development of skin 

 cancer by 20-methylcholanthrene (Bickis, Estwick and Campbell, 1956). Hypophysecto- 

 mized rats given growth hormone apparently do not show the inflexion in the S-shaped 

 curve of weight growth which is found in normal growth (Fig. 25). 



If the growth cycles mentioned are taken into account, the growth e.g. of the 

 mouse and rat can be reproduced with excellent approximation by equations 

 (5.28) and (5.29) (Figs. 26, 27). 



10 20 30 

 Time in weeks 



Fig. 27. Growth of the white mouse (cJ)- Robertson's data. The solid line indicates mean 

 values, the shaded zone the double probable error. This growth curve was approximated by 

 Robertson by superposition of not less than 4 curves with a profusion of arbitrary constants. 

 It can be fitted as well by equation (5.28), p. 190, only. After Bertalanffy, 1938 and 1951a. 



Literature p. 253 



