174 GROWTH OF PARTS AND ORGANS 



(2) For the female 



Tail length = 0.824 Bd. I. +43.1 log (Bd. I.) -98.4 (51) 

 Formulas (50) (51) were used for table 85. 



Brain Weight on Body Weight, Norway (Donaldson and Hatai, '11) 



Brain weight (sexes combined) =0.825 log (Bd. wt. —4) +0.233 (52) 



This formula applies only to rats 5 grams or more in body- 

 weight. To obtain the weights for the male the values given 

 by the formula are increased by 1 per cent, and to obtain the 

 weights for the female, they are decreased by 1 per cent. 



Formula (52) with corrections mentioned above used for 

 table 85. 



Cranial Capacity on Body Weight, Norway (Donaldson, '12) 



Cranial capacity in cc. (sexes combined) = 



0.00105 Bd. wt. +0.548 log Bd. wt. +0.476 (53) 

 [80 < Bd. wt. < 380] 



Spinal Cord Weight on Body Weight, Norway (Donaldson and Hatai, '11) 



Spinal cord weight (sexes combined) = 



0.724 log (Bd. wt. +30) - 1.082 (54) 



To obtain the weights for the male the values given by the 

 formula are increased by 0.15 per cent, and to obtain the weights 

 for the female they are decreased by 0.15 per cent. 



Formula (54) with corrections mentioned above was used for 

 table 85. 



