WEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 



KM) 



i.05 



'.•."♦ •• " . '•♦.»••,,/. •* • ••..7 



.30 



20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 

 Body weight In grams 



Fig. 2 Chart showing the change in the ratio of tail-length to body (nose-anus) 

 length in the albino rat from birth to maturity. Males are indicated by rounded 

 dots, females by X. The individuals held at constant body-weight during the 

 experiment are encircled. The curve is drawn through points representing the 

 means for the normal individuals at various periods, sexes combined. 



(by dropping out the lighter rats of the series given in table 

 3 a) . Thus in sixteen normal males aged three weeks, average 

 net body-weight is 24.2 grams, the average body-length is 94.5 

 mm. and tail-length is 61.6 mm. (compared with 105.2 mm. 

 body-length and 86.2 mm. tail-length in the 3 to 10 weeks experi- 

 ment). Similarly, in eight normal females at three weeks, aver- 

 age net body-weight 23.2 grams, the average body-length is 

 91.1 mm., and tail-length is 63.4 mm. (compared with 99.6 mm. 

 body-length and 83.9 mm. tail-length in the 3 to 10 weeks 

 experiment). In other words, while the body has increased 

 about one-tenth in length, the tail has increased over one-third, 

 the body-weight being held constant from the age of three to 

 ten weeks. 



