310 GROWTH IN WATER AND SOLIDS 



weight deviates from the table value. The correction factor is the 

 same for both sexes and for a difference + or - of 0.001 gram 

 in brain weight is respectively - or + 0.0013 per cent of water. 

 The computed correction for the percentage of water is added 

 to the table value in the case of a small (light) brain and subtracted 

 in the case of a large (heavy) brain. These corrections do not 

 apply to brains from rats less than 20 days of age, nor to excessive 

 differences (more than ± 15 per cent) in brain weight. By the 

 same procedure correction may be made for the percentage of 

 water in the spinal cord according to its absolute weight. Table 

 165 gives the factors to be used. 



Body weight not normal to age. Finally there is the not infrequent 

 instance of body weights which depart widely from those for 

 given ages in table 157. Where this departure is in excess the 



TABLE 165 

 Albino rat. CJiange in the percentage of ivater for each 0.001 gram of spinal cord 

 weight a.s obtained from the comparison of the light and heavy cords in the same 

 age group 



absolute brain weight is that to be expected for the body weight. 

 In this instance the percentage of water in the brain or cord 

 characteristic for the age is to be taken as the basal value and 

 corrected according to the deviation in the weight of the brain 

 or cord by the use of the respective correction factors given under 

 "Body weight normal to age." 



A corresponding procedure applies m the case of rats with body 

 weights low for age. 



Correction according to sex. According to table 157 after 28 

 days of age the brain^ — ^and after 62 days the spinal cord also, 

 weigh less in the female than in the male of like age. 



When a comparison of the respective percentages of water is 

 made after these limiting ages it is found that this is higher in 

 both the brain and the cord of the female. 



