C. M. JACKSON 



GROWTH AND VARIABILITY OF THE BODY 



1. Growth in body weight 



The data presented in this paper are inadequate for a complete 

 discussion of the growth of the body as a whole. Certain phases, 

 however, may be noted. Donaldson ('06) has made numerous 

 observations upon the postnatal growth of the albino rat, on the 

 basis of which he has drawn certain conclusions, with which the 

 present data may be compared. Table A shows the average 



TABLE A 

 Average gross body weight of albino rat at various ages, sexes separated^ 



Jackson's larger 



SERIES 



Jackson's smaller 



SERIES 



DONALDSON S SERIES 



(1906) 



newborn < 



7 days 



3 weeks 



6 weeks 



10 weeks 



5 months 



1 year 



(63 m. 



(66 f. 

 (36 m. 

 (64 f. 

 (53 m. 

 (59 f. 

 (45 m. 

 (50 f . 

 (23 m, 

 (25 f. 



5.13 



4.89 



10.53 



10.29 



23.99 



21.50 



63.72 



64.25 



130.4 



108.9 



(44 m. 

 (43 f. 

 (30 m. 

 (27 f. 

 (24 m. 

 (25 f. 

 (22 m. 

 (20 f. 

 (20 m. 

 (23 f. 

 (20 m. 

 (21 f. 

 ( 5 m. 

 (20 f. 



5.06 

 4.82 

 10.61 

 10.48 

 22.20 

 17.01 

 52.89 

 54.86 

 121.9 

 103.3 

 167.5 

 142.1 

 213.0 

 163.7 



(40 m. 



(17 f. 

 (11m. 

 ( 8f. 

 (19 m. 

 (17 f. 

 (19 m. 

 (17 f. 

 (19 m. 

 (11 f. 

 (19 m. 

 (11 f. 

 (6 m. 

 ( 7f. 



5.4 



5.2 



9.2 



8.7 



21.2 



22.6 



46.3 



47.9 



106.6 



99.8 



225.4 



184.6 



279.0 



226.4 



1 Jackson's observations listed under '3 weeks' were nearly all at 20 days, and 

 those of Donaldson under '6 weeks' were at 43 days. The females were unmated, 

 excepting all of Donaldson's series at 1 year, and a part of Jackson's series at 1 

 year. 



gross body weight in each sex at various ages in my larger series 

 (recorded in table 1), in my smaller series (dissected for the 

 organs), and in those observed by Donaldson at corresponding 

 ages. 



From table A it is evident that the rats used in the present 

 study averaged somewhat smaller at birth for both sexes than 

 those of Donaldson, but show a more rapid growth during the 

 first week, so that at seven days their average weight is greater. 

 At three weeks the males in Donaldson's series average somewhat 



