WEIGHTS OF BRAIN AND CORD 



201 



Using this formula the brain weights have been computed for 

 each of the series of body weights as determined by formulas 

 (47) and (48). 



It has been found however (Donaldson and Hatai, '11, p. 428) 

 that the weight of the male brain is one per cent above the mean 

 for the two sexes, and that of the female, one per cent below. 



Chart 31 Norway rat, giving brain weight on the body weight. Males only. 

 With the corresponding graph for the Albino inserted for comparison. Formula 

 52, table 85. Also the spinal cord weight on the body weight. Males only. With 

 the corresponding graph for the Albino inserted for comparison. Formula 54, 

 table 85. 



As a consequence, each value gotten by the foregoing compu- 

 tations has been corrected by adding one per cent to the value 

 found to give the weight for the male brain and by subtracting 

 one per cent to obtain the weight for the female brain. 



Chart 31 gives the graph for the male brain weight on the 

 body weight and the corresponding graph (male) for the Albino 

 (see chart 9) is also drawn for comparison. The marked differ- 

 ence in the brain weight of the two forms is clearly shown. 



