304 THE SIZE AND WEIGHT 



up of weights which are above the average of the healthy 

 brain, and of others which are materially below it." In 

 general the latter greatly preponderate, and therefore it is 

 that the average is low ; but among Epileptics in asylums, 

 and occasionally among simply demented patients, the 

 brain has not unfrequently been found to be considerably 

 above the normal or average weight for sane individuals. 



In congenital Imbeciles and Idiots the average weight 

 of the brain is still lower than it is among those in whom 

 Chronic Insanity has supervened during adult life. From 

 an examination of twenty-two brains of idiots, some of 

 whom were also epileptics, Dr. Thurnam obtained an 

 average weight for fourteen males of 42 oz., or 1,190 

 grammes, and for eight females a weight of 41*2 oz., or 

 1,167 grammes. The average of the latter is curiously 

 enough almost identical with that of the rest of the 

 female insane of the same series; though that of the 

 male brains is very decidedly less. Idiocy is, therefore, 

 not necessarily associated with a very small size of brain : 

 though this is frequently the case, still various deficiencies 

 in the internal structure and finer development of the 

 brain may also entail a similar condition of mental defect. 



Among 50 brains of Idiots examined by Dr. Langdon Down, whose 

 ages ranged from 5 to 33 years, the minimum weight in a boy of 18 

 was 15 oz. (425 grammes) ; the maximum weight in a man of 22 

 was as much as 59'5oz. (1,404 grammes). The latter weight was 

 in all probability one which had been augmented to a considerable 

 extent by morbid tissue changes of a kind to which reference will 

 presently be made. 



Where the weight of the Brain falls below a certain 

 minimum standard, the possession by its owner of any- 

 thing like ordinary Human Intelligence seems to be 

 impossible. Gratiolet, without specifying the sex, sup- 

 posed this lower limit of weight to be about 31 J oz., or 



