NERVOUS SYSTEM 



309 



graphs in chart 55. The data for the first 10 days are from 

 direct observations. The percentage of water in the brain and 

 spinal cord is linked with age and is not readily modified by 

 nutritive conditions, nevertheless lung disease tends to lower 

 the percentage of water in both the brain and the cord. King 

 ('11). Degener ('22). 



Chart 55 Showing the percentage of water on age in the central nervous sys- 

 tem of the male albino rat. The upper graph gives the values for the water in 

 the brain as determined by the formulas (Hatai in 'The Rat,' Donaldson, 1915). 

 The lower graph gives the corresponding values for the spinal cord determined 

 in the same way. The small black dots indicate for the brain the corrected 

 (observed) values for the several age groups, and these corrected values form the 

 data on which the formulas have been based. The small black triangles have a 

 like significance in relation to the spinal cord, (Donaldson '16). Formulas: 

 Brain: (47)- (49 a), spinal cord: (50)-(52 d). Table 157. 



4. Correction for the percentage of water according to the absolute 

 brain weight in each sex. Body weight normal to age. Brains 

 low in weight for the body weight on age (as shown in table 157) 

 tend to have a higher percentage of water than appears there. 

 Similarly, brains high in weight tend to have a lower percentage 

 of water. When using table 157 for reference, correction may be 

 made for the absolute brain weight at a given age when this 



