ALBINO RAT VISCERA, GLANDS, EYEBALLS: WEIGHTS 99 



Or expressing the body weight in terms of body length, we have 



Body length +134 



Body weight = 10 ^^^ _ 15 



2. Under some conditions the growth of rats is considerably 

 accelerated in both body weight and body length for given ages. 

 Such rats show generally a marked disproportion in the weight 

 relation between body and organs; that is, the viscera are, as it 

 were, overgrown by the remainder of the body. In such cases 

 the body weight normal for the viscera may be estimated from 

 the weight of any one of the organs, such as the weight of the 

 heart. Thus one determines the body weight from the observed 

 heart weight, and then compares the weights of the other organs 

 as observed with those computed for the body weight thus 

 obtained. 



3. In any experiment where the controls are compared with 

 experimented animals, modifications in the experimented group^ 

 can be determined in the following manner: First determine the 

 percentage deviation of the controls from the calculated values 

 as given by the formulas and then the corresponding percentage 

 deviation of the experimented animals. The algebraical differ- 

 ence of the two values thus obtained will be the difference 

 between the experimented and controls. This method is im- 

 portant when the body weights of the two groups of rats (experi- 

 mented and controls) differ widely since the weight relations 

 between body and organs are not constant but vary with the 

 change in body weight. 



We now turn to a brief description of the formulas^ for the 

 weights of the viscera and the graphs which represent them. 



1 In order to bring together all the formulas which so far have been worked 

 out in connection with the albino rat the following additional formulas are in- 

 serted here. This addition will, I believe, be very convenient for reference. 



Weight of braiii = 0.569 log (Bd. wt. - 8.7) + 0.554 [Bd. wt. > 10] 



Weight of spinal cord = 0.585 log (Bd. wt. + 21) - 0.795 



Tail length, male = 0.853 Bd. wt. + 38.8 log Bd. wt. - 90.5 



Tail length, female = 0.874 Bd. wt. + 43.2 log Bd. wt. - 98.1 



