110 
Brain-weight and Head-size 
The maximum, average and minimum weights of the brain, in four groups, 
arranged according to age and sex, of the ' post-mortem ' room subjects of the 
Middlesex Hospital, may be seen in the following table : 
The weight of the brain is expressed in grammes, and each group contains 50 
subjects. 
Age 
Males 
Females 
Max. 
Aver. 
Min. 
Max. 
Aver. 
Min. 
20—46 
46 upwards ... 
1635 
1588 
1370-5 
1316-1 
1207 
1120 
1520 
1408 
1223-5 
1195-7 
1027 
955 
It will be noticed that in passing fi'om the younger to the older groups 
there is a decrease in the average brain-weight of 54-4 grm. in the male, and of 
27-8 grm. in the female, the mean decrease for both male and female being 
approximately 40 grammes. 
This result corresponds very closely with the table compiled from the observa- 
tions of R. Boyd, and published in Quain's Anatomy, Vol. ill. Part I. p. 178, in which 
it is shown that " the brain is absolutely heavier between 14 and 20 years of age 
than at any other period of life, and that at the age of 80 it has lost about 90 
grammes, or rather more than 3 ozs., i.e., of its total weight." 
Not only is there a marked change in brain-weight corresponding with different 
periods of life, but there are also considerable variations in the thickness of the 
skull and its coverings. 
The scalp is thin in infants and young children, and a sensible attenuation 
of the scalp occurs in old age, which is probably largely due to atrophy of the hair 
follicles following the loss of hair. The amount, although small, is measui-able, 
and is sufficient to affect the general result of a statistical investigation. The 
amount of atrophy may be seen by a comparison of the figures in the following 
tables, which show the average differences between the diameters of the head and 
the diameters of the skull as measured before and after the scalp has been turned 
down in order to remove the ' skull cap.' 
18 Males hettueen 20 and 46 years of age. 
mm. 
Heiglit of head minus height of skull = 4-05. 
Length „ ,, length „ =8-47. 
Breadth „ „ breadth „ =8-27. 
27 Males from 46 years upward. 
mm. 
Height of head minus height of skull = 3 -79. 
Length „ „ length „ =7-25. 
Breadth „ „ breadth „ =7-40. 
