For women, Boyd gives the following figures:

THE GROWTH OF THE BRAIN IN WOMEN
(Figures Given by Boyd)

AgeWeightProportion to the maximum reduced to 100
At birth28322.8
Three months45236.5
From 3 to 6 months56045.2
From 6 months to 1 year72858.8
From 1 to 2 years84468.1
From 2 to 4 years99180.8
From 4 to 7 years1,13691.7
From 7 to 14 years1,15593.3
From 14 to 20 years1,244100.4
From 20 to 30 years1,238100.0
From 30 to 40 years1,21898.3
From 40 to 50 years1,21397.9
From 50 to 60 years1,22198.2
From 60 to 70 years1,20797.4
From 70 to 80 years1,16794.2
From 80 to 90 years1,12590.8

The rhythm of growth of the female brain is analogous to that of the male, except for the more precocious attainment of the maximum weight, which corresponds to the more precocious evolution of the female organism.

It should be noted that in the tables above cited the maximum is actually given as occurring at the age of twenty; and that after this period the weight diminishes again, subsequently increasing up to an age that varies according to the sex. But this maximum at the age of twenty must be considered as one of the false results of mean averages; and it must be explained on the ground that after the twentieth year the death rate has eliminated a series of individuals whose heads were abnormally large, and that a majority of the survivors were those whose heads had developed within normal limits.

This fact is further confirmed by Wagner's figures, cited by Broca:

MEAN WEIGHT OF THE BRAIN
(According TO Wagner)

AgeMenWomen
Under 10 years9851,033
From 11 to 20 years1,4651,285
From 21 to 30 years1,3411,249
From 31 to 40 years1,4101,262
From 41 to 50 years1,3911,261
From 51 to 60 years1,3411,236
Above 60 years1,3261,203

Here again we have a false maximum at twenty, which nature subsequently corrects through mortality.

From such knowledge we obtain certain important rules of hygiene.