506 FRETS, THE INDEX CEPHALICUS. 
Sometimes the index of a child increases a little during 
the growth. 
In the first year of life the modificability of the head is great. 
So with weak children one may find a high index that after one 
or two years decreases. Little differences may also be accidental, 
for measuring children is more difficult than adults.1) It is of 
interest that extreme indices in general are preserved. 
We now have to make a remark on the relation of skull- and 
headindex. Of a few families for one of the parents I only dispose 
of the skullindex. These cases always concern the deceased of 
the asylum, often emaciated and worn-out individuals. Usually the 
headindex is diminished with two units to get the skullindex 
(DENIKER, 1900). This is also advised by Fiirst (1902, p. 87). I 
have done a series of observations with the obductions. Table 12 
contains the figures of 57 cases. For the average difference of 
head- and skullindex was found M = 0.78 and cs = + 0.695. 
According to these observations the amount with which the head- 
index has to be diminished to get the skullindex is very variable 
and does not exceed 1.5 units. 
Fiirst’s observations vary in a high degree also. Diminishing 
the headindices of his material with 2 units he gets a too low 
skullindex. 
From the measurements done by GLADSTONE (1905 p. 110) of 
the thickness of the scalp with men and women at different ages 
I calculate that with males and with females the index has to be 
diminished with one unit. The differences, between men of 20—46 
years of age and men 46 years of age and upward, of the correction 
from head- to skullindex are very slight. WELCKER and MERKEL 
observed that the thickness of the scalp is 5.5 mm (LEE 1901, 
9.2251). 

1) See. also PEARSON 1911, p. 78. The personal equation element in the 
process of headmeasurements will be rather large. This will be true espe- 
cially with measurements of thickness of scalp of post-mortem objects and 
with headmeasurements of young children. The same person also will not 
always get the same results in the course of some years. I myself f. i. got 
in the 2" and 3° year of this inquiry several times somewhat smaller values 
for the headlength and the headbreadth, because I exercised then a little 
more pressure with the compasses. I did so under influence of head- == 
skullmeasurements with post-mortem objects. 
