92 CM. JACKSON 



experiment (gross bod}^ weight, 244 grams). Since the average 

 loss in bod}^ weight during the inanition period is one-third, it is 

 evident that the brain has lost but little if any in absolute weight. 



The theoretical average initial absolute weight of the brain is 

 about 1.902 grams, forming 0.78 per cent of the (gross) body 

 weight (Donaldson '09). Accordmg to Donaldson's ('08) table 1, 

 the brain weight observed in six cases averaged 1.900 grams, the 

 theoretical being 1.905 grams, at the body weight of 245 grams. 

 If this absolute weight of the brain remained constant, while the 

 body weight lost one-third (33.9 per cent), the final percentage 

 weight of the brain would be increased about one-half, or to 

 1.17 per cent. The average absolute weight of the brain actually 

 observed at the end of the period of acute inanition is 1.8046 

 grams, corresponding to an average of 1.18 per cent of the (net) 

 body weight.^ This weight is slightly less than would be expected 

 if the brain remained constant in absolute weight, indicating a 

 loss of about, 5.1 per cent in the absolute weight of the brain 

 during inanition. 



The observations upon the brain in chronic inanition (table 3) 

 indicate a similar condition. The average brain in this series 

 weighs 1.743 grams and forms an average of 1.33 per cent of the 

 (net) body weight. (This is the mean of the individual percent- 

 ages; 1.743 grams would form 1.31 per cent of the average net 

 body weight, 132.5 grams; or 1.28 per cent of the average cor- 

 responding gross body weight, 136 grams.) According to calcu- 

 lations from Donaldson's ('09) data, the average brain corre- 

 sponding to the body weight at the beginning of the experiment 

 (213.7 grams) should weigh 1.866 grams, forming about 0.87 per 

 cent of the body weight (the percentage being higher than in the 

 acute inanition series on account of the smaller average body 

 weight).^ This is slightlj^ higher than the result to be expected 

 on the assumption that the absolute brain weight has remained 



' This is the mean of the individual percentages, as shown in table 3. The 

 average brain weight, 1.8046 grams, w^ould correspond to 1.13 per cent of the cor- 

 responding average gross body weight, 160 grams, at the end of the experiment. 



^ According to Donaldson's ('08) table 1, corresponding to a body weight of 

 215 grams, the average of 8 brains, both sexes, was 1.873 grams, the corresponding 

 theoretical weight by formula being 1.871 grams. 



