35^ journal of Comparative Neurology and Psychology. 



mentally, do not modify essentially the relations of the spinal cord 

 to the body, so that the weight of the cord as calculated by the 

 formula [3] corresponds closely with that observed (see table 3). 

 From the foregoing observations we conclude therefore : 



1. That for albino rats between 5 and 315 gms. in body weight, 

 the mean weight of the spinal cord as observed, increases from 

 .036 gm. to .737 gm, or 20.4 times, and as calculated from 

 0.33 gm. to .683 gm. or 20.6 times. 



2. That from birth to a body weight of about 205 gms. the 

 spinal cord grows rapidly, and after that more slowly, increasing 

 in this phase of slow growth nearly as the 2.7th root of the body 

 weight. 



3. That the weight of the spinal cord is closely correlated 

 with the body weight, the coefficient of correlation being 0.8564 



± 0.0071. 



4. That the relation of the spinal cord weight to the body 

 weight, is not essentially modified in either "dwarf" or "giant" 

 individuals, nor in those experimentally stunted. 



5. That in these various relations there is no marked distinc- 

 tion between the sexes, although on the average, the female spinal 

 cord is about 2 per cent heavier than that of the male. This 

 difference probably depends in part on the effect of the bearing 

 of young. 



THE ENTIRE CENTRAL NERVOUS SYSTEM. 



While a detailed discussion of the weight relations of the entire 

 central nervous system of the albino rat is hardly necessary, in 

 view of what has already been presented concerning the brain 

 and the spinal cord, nevertheless one or two points call for con- 

 sideration. 



The values for the entire central nervous system are entered 

 in table 5, in which the sum of the values for the brain and the 

 spinal cord are given both as observed and as calculated by the 

 formulae [i] and [3]. The totals for the entire series of groups 

 agree closely, the observed being 0.2 per cent less than that cal- 

 culated by the formulae.. By dealing with the entire system, we 

 avoid any error which might depend on variations in the point of 

 separation between the brain and the spinal cord. 



On determining the period of rapid growth for the entire nervous 

 system and using the same general procedure as before (see pp. 



