Hatai, Nervous System of Albino Rats. 153 



in the stunted rats the ratio is i : 0.75. Underfeeding therefore 

 produces short tailed individuals. The nature of this result has 

 still to be investigated. 



Central nervous system. — The weight of the brain and spinal 

 cord and the percentage of water in both were separately deter- 

 mined according to the usual procedure. 



The weight of the encephalon was found to be normal to the 

 body weight in both the controls and stunted rats, the brain 

 weight of the first controls is heaviest and that of the "stunted" 

 and "second controls" follow in the order named. The relation 

 between body and brain weights was tested by the formula, 



Brain weight = 0.554 + 0.569 log (body weight — 8.7). 



This formula has been developed through the study of our labor- 

 atory records and gives us the theoretical weight of the brain 

 for any body weight. The former was found to be normal even 

 in the stunted group. As seen from the table, the difference 

 between calculated and observed brain weights on the average 

 was about 1.5 per cent, indicating a normal relation of the brain 

 weight to the given body weight. Thus we conclude that the 

 normal relation between the body and brain weights was not dis- 

 turbed by stunting. 



We have as yet no satisfactory method for determining the 

 normal weight of the spinal cord in respect to either body weight 

 or any other characters. Nevertheless the proportional weight 

 of the spinal cord in the experimented and in the second control 

 rats with respect to the brain and body weights suggests that it 

 also has grown normally (see Table I). Therefore we conclude 

 that the weight of the spinal cord and brain are similarly related 

 to the body weight. Consequently so far as the weight of the 

 central nervous system is concerned, the normal relation to the 

 body weight is still maintained by the stunted rats. 



It is interesting to note in this connection that the definite rela- 

 tion between the body and brain weights is not disturbed even 

 when the growth of the body has been considerably accelerated by 

 means of the lecithin- or when the rats have been once starved 

 and then returned to normal diet so that the final body weights 



^ The effect of lecithin on the growth of the white rat. American Journal of Physiology, vol. lo, 

 no. I. 1905. 



