IN THE DIFFERENT RACES OF MAN. 
527 
Number 
of 
cases. 
Sexes. 
Ages. 
Capacity 
of skulls. 
Estimated 
weights of 
brains. 
Actual weights of 
brains, without 
membranes, fluids, 
and medulla 
oblongata. 
With the addition 
of 14 grms. for the 
medulla oblongata. 
Differences between 
estimated weights 
and actual weights. 
The former more 
than the latter -j-, 
less than the latter — . 
5 
75 
9 
11 
100 
15 
115 
6 
6 
6 
6 
6 
$ 
<S and $ 
10 to 19 years 
20 to 29 years 
30 to 59 years 
60 to 90 years 
10 to 90 years 
cub. cent. 
1436-62 
1535-52 
1556-96 
1550-43 
1533- 11 
1318-30 
1505-09 
grms. 
1270-06 
1355-11 
1374-95 
1349-44 
1352-27 
1165-16 
1329-59 
grms. 
1209-85 
1327-43 
1316-12 
1227-21 
1310-06 
115965 
1290-44 
grms. 
1223-85 
1341-43 
1330-12 
1241-21 
1324-06 
1173-65 
1304-44 
grms. 
46-21 + 
13-68 + 
44-83 + 
108-23 + 
28-21 + 
8-49- 
25-15 + 
The results of these tests of our rule of a tare of 15 per cent., for so the experiments 
of Dr. Weisbach may be regarded, are that in each of the groups into which the ages 
are divided our estimated weight exceeds the true weight of the brain, except in the case 
of the brains of the 15 women. In these the estimated weight falls short of the actual 
weight by an average of 8‘49 grms., or nearly *30 of an ounce. The other groups stand 
thus, ascending from the lowest to the highest. In 75 men from 20 to 29 years of age, 
that is, in the vigour of life (and it is to this period of life that the great majority of the 
skulls of the preceding race-Tables belong), the estimate exceeds the true weight by only 
13-68 grms., or about half an ounce. In the whole number of cases taken together, the 
excess of the estimate is 25T5 grms., or about -90 of an ounce. In the entire group of 
males this excess is 28-21 grms., or as near as may be one ounce. In the 9 males from 
30 to 59 years of age, when it seems that the brain begins to have an increment in its 
fluids, it rises to 44-83 grms., or a trifle more than an ounce and a half. Before this 
organ reaches its maturity, as in the group of males from 10 to 19 years of age, the 
excess of our estimate is almost the same, viz. 46-21 grms., or somewhat above an ounce 
and a half, which shows the large amount of serosity in the brain at this early period of 
life, when the organ is in a state of active growth. But it is in advanced life, when this 
serosity again abounds, that our estimate is most remote from the actual weight of the 
cerebral mass itself. Here the discrepancy amounts to 108-23 grms., or approaching 
to 4 ounces. 
It must be recollected that, although our general rule is of great value in estimating 
the true weight of the brain from the capacity of the skull, where we have a large 
number of specimens of different sexes and ages before us, and is perhaps as near as any 
general rule that can be laid down, it is not to be expected that any uniform rate of 
deduction can be devised which will be correct even in the majority of individual in- 
stances, where the causes of deviation are so varied and complex. The complete test to 
which our rule has been put by these 115 careful experiments on brains of very different 
ages, shows its value and general correctness in a more satisfactory manner than could 
have been anticipated. If further investigations should prove that Dr. Weisbach’s 
observations may be taken to possess an average value, it will probably be desirable to 
increase our rate of tare to a slight extent. 
mdccclxviii. 4 d 
