1 66 'Journal of Comparative Neurology and Psychology. 



234 grams 209 mm. 



Y8 grams 147 mm. 



Difference 02 mm. 



Percentage gain, 42 per cent. 



It appears, therefore, that while the sitting height in man increased 

 47 per cent during the greater portion of the active growing period, 

 the body length in the rat increased 42 per cent during the cor- 

 responding period. 



Though not exactly alike, these tigures represent changes of the 

 same order, and this is all that we desire to show at the present 

 time. The value of this determination, so far as it can be foreseen, 

 is to indicate that the spinal cord during growth is subject to 

 approximately the same relative amount of passive lengthening in 

 both man and the albino rat. 



Conclusions. 



1. In the albino rat the ratio obtained by dividing the body 

 weight by the body length diminishes as the body weight in- 

 creases. 



2. Among rats of the same body weight, the males have a slightly 

 greater body length than the females. 



3. The correlation between body weight and body length is high, 

 being .90. 



4. The correlation between body length and l)rain weight is high, 

 being .86. 



5. The correlation between body length and the weight of the 

 spinal cord is nearly perfect, being .99. 



6. The greater weight of the central nervous system in male, 

 as compared with female rats of like body weight, is completely 

 explained by the greater body length of the males. This result 

 agrees with the more recent observations on man. 



7. The relative increase in the body length of the' rat during 

 active growth is similar to the increase in the sitting height of 

 man during the corresponding period. Hence, in both forms, the 



