98 C. M. JACKSON AND C. A. STEWART 



MATERIAL AND METHODS 



The white or albino rat (Mus norvegicus albinus) was used 

 in the experiments, for which it is in many respects well adapted. 

 It is hardy and thrives in captivity. It breeds rapidly (period 

 of gestation three weeks), reaches sexual maturity at ten weeks, 

 and adult size within a year. The normal growth rate and 

 variability of the albino rat and its various organs have also 

 been very thoroughly worked out, chiefly by Donaldson, Hatai. 

 Jackson, and Lowrey, and normal growth tables by Donaldson 

 ('15) are available for comparison. Moreover, the effects of acute 

 and chronic inanition upon the weight of the body and of the 

 various organs in the rat at different periods have been studied 

 by Jackson ('15, '15 a), Stewart ('16, '18, '19), and Jackson 

 and Stewart ('18, '19). The data available from these studies 

 make possible a comprehensive view of the effects of inanition 

 at various ages and the rapidity of recovery upon refeeding in 

 an organism whose normal growth rate and variability are well 

 known. The lack of such data frequently makes it impossible 

 to draw trustworthy conclusions from the results of experi- 

 mental work, especially when the observations are limited in 

 number. 



In the present investigation, thirty-eight litters of albino, 

 rats from the colony in The Institute of Anatomy were used. 

 About half of the rats died from starvation during the experi- 

 ments and are excluded from consideration. One hundred and 

 thirteen rats survived, including 35 male and 35 female test 

 rats, with 27 male and 16 female normal controls. In general, 

 test rats and controls were available from each litter, as shown 

 by the data in table 1. In this table, the letters 'St' (Stewart) 

 refer to the series to which the rat belonged, the number pre- 

 ceding the decimal point indicates the litter, and the number 

 following designates the individual. The final letter 'm' indi- 

 cates male, or 'f,' female. 



As further shown in table 1, the experiments may be divided 

 into (A) those in which the preliminary underfeeding began at 

 birth, and (B) those beginning at three weeks of age. The rats 



