130 HENRY H. DONALDSON 



stopped by the underfeeding, which stops the growth as indicated 

 by the body weight and the brain weight, we should have found 

 the higher percentage in the experimented rats. 



As further evidence that the disturbance of the growth process 

 involves but slightly the changes in the percentage of water corre- 

 lated with increasing age, we have the data in this same paper 

 by Hatai given in Table IV, series II where the control group was 

 killed and examined at the beginning of the experiment. Here the 

 percentages are 



79.01 for the control rats 

 78.71 for the experimented rats 



giving a difference of 0.3 per cent. 



The difference in this case is greater than in the preceding 

 because not only is the percentage of water in the experimented 

 group slightly diminished by the treatment, but also because the 

 experimented group was three weeks older than the controls at 

 the time of killing, thus giving a total loss of 0.3 per cent in series 

 II against 0.2 per cent in series I, where both controls and experi- 

 mented rats were killed at the same time. This again supports 

 the view that underfeeding does not arrest the changes in the 

 percentage of water characteristic for advancing age, but may 

 rather hasten them. 



The weight of water in the brain and spinal cord. The preceding- 

 descriptions have been given in the terms of the percentage of 

 water. A better view of the changes taking place can be obtained 

 however by following the suggestion of my colleague, Dr. Hatai, 

 and showing the changes in the absolute weight of the water in 

 the brain and cord at different weights of these parts. This 

 eliminates the time factor which has modified the previous 

 forms of presentation, and gives a simple and suggestive picture of 

 the changing relations between the water and the solids. 



The determinations thus made are given in table 5 and have 

 been also plotted in charts 4 and 5 



The following table 5 shows that for the successive increments 

 of weight, the female brain has less water than the male brain 

 of like weight. This is undoubtedly due to the fact that under 



