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An examination of the Breitinger method of cranial capacity determination.

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AN EXAMINATION OF THE BREITINGER METHOD
O F CRANIAL CAPACITY DETERMINATION
T. D. STEWART
Division of Physical Anthropology, 17. S. National Muaeum
At the present time the determination of cranial capacity,
despite the countless efforts at refinement, offers greater
chances for error than most other measurements generally
taken by craniometrists. If this measurement is worth taking
at all, and probably no one will deny that it is, there should
be available a standard method that is both simple in its
procedure and reliable in its results. Until this point is
reached there will continue to be a lack of confidence in the
records.
During the past year (’36) Breitinger published a method
for which he claims both simplicity and reliability. He states,
moreover, that
numerous repetitions of the measurement by observers who
used the method for the first time, showed almost as small an
observational error [as his own], and therewith demonstrated
that this technique, given personal demonstration-which is
indeed indispensable for all methods of measurement-ensures
the desired reliability and exactness in other hands too (p.
144).
Regardless of the value of personal instruction in anthropometry, a continuity of this instruction is not entirely feasible, and hence I feel that it is desirable to subject this method
to the severer test of being employed by one who has only the
printed instructions to follow.
That I have undertaken this project is due largely to the
urging of Miss M. L. Tildesley of the “Comit6 de standardiAlso, i t must be
zation de la technique anthropologique.”
’ I am indebted to Miss Tildeeley for supplying me with a translation of
Breitinger ’8 paper.
111
AYBRICAN JOUENAL OF PEYSICAL ASTHROPOXLIGT, VOL. XXIII, NO.
JGLY--SEPTEMBER, 1937
1
112
T. D. STEWART
admitted, my willingness to do this work was influenced by
my interest in cranial capacity as a result of having published
recently (’34) on the general subject.
GE-NXRAL PRINCIPLES
It is evident from Breitinger’s paper that he has clearly
recognized the general principles involved in the determination of cranial capacity. However, like others, he has not,
in my opinion, placed sufficient emphasis upon them. Before
outlining his method it may be well, therefore, to state briefly
some of these principles. I believc. all will agree that the
following a r e the most important:
1. Any standard technique for filling the skull must reproduce a certain density of the filling material (seed) as constantly as possible.
2. The density of seed in a skull of unknown capacity can
only be inferred from previous experience with the same
filling method on standard skulls (crtnes 6talons).
3. To obtain the capacity of a skull by use of a measuring
cylinder the density of the seed in both cylinder and skull must
be the same.
4. The density of seed resulting in a measuring cylinder
when the latter is used in combination with a funnel depends
chiefly on four factors: a) the size of the seed, b ) the type of
funnel (slope of side and width of opening), c) the distance
the seed fall, and d ) the diameter of the cylinder. Larger
seed2 flowing a t a slower rate (narrower funnel opening)
from a greater height and into a narrower cylinder all contribute to an increased density.
METHOD
The method advocated by Breitinger, using mustard seed,
is a n adaptation of that of Mollison (’32) designed for the
use of rape seed (‘Riibsamen’). Briefly, Breitinger determined the density given by his cylinder-funnel combination
As compared with smaller eeed of the aame kind; for instance, large and small
mustard seed.
CRANIAL CAPACITY DETERMINATION
113
(principle 4, above) and worked out a technique for filling
the skull that gave this same density (principle 3) fairly
constantly (principle 1). The preliminary testing was done,
of necessity, on a standard skull (principle 2).
The cylinder in use had an interna.1 height of 50 cm., and
a n internal diameter of 73 mm. The funnel had a slope of
60” (“sein Vertikalriss ein gleichseitiges Dreieck darstellt”)
and a 15 mm. opening. With ‘top medical quality’ mustard
seed this combination produced a density of 767 gm./1000 cc.
(0.767).
To reproduce in the skull this density of seed Breitinger
developed the following procedure (literal translation, p. 147) :
1. Bed skull on pad, frontal obliquely downward.
2. Pour in the mustard seed through funnel ; the seed level
should be kept u p to one-third the height of funnel; through
gentle tilting of the skull on its bed the seed which fill the
funnel to this level when they have stopped running will all
flow into the skull.
3. Shake the skull with the hands laid on flat, frontal obliquely down; rate: four movements back and forth per
second; duration: a) 15 seconds holding skull by frontal and
occipital; b) 15 seconds holding skull by the sides.
4. Pour more seed in slowly straight from jar ; at the same
time tilt skull on the bed in all directions with the left hand.
5. Distribute the masses of seed by probing six times with
the wooden stick: once each slanting forward and to the
right, sideways and to the right, backward and to the right,
and similarly for the left.
6. Again slowly fill up from the j a r with a simultaneous
tilting of skull on its bed.
7. Distribute seed for the last time with the thumb; fill in
to the edge of the foramen magnum.
8. Empty contents of skull into funnel which has been set
in position on cylinder ; fill funnel completely.
9. Let it run steadily into cylinder.
‘This stick is not described, but is assumed to be the same as tlint figured by
Mollison; namely, 20 mm. in diameter mid rounded a t the ends.
114
T. D. STEWART
More details are given in the text (pp. 142-143), but the
above will suffice to orient the reader.
Circumstances warranted the following changes in this procedure for the purpose of the present tests :
a) Instead of placing the skull on a pad and filling by means
of the Mollison funnel (steps 1, 2 and 4), the skull was held
at a n angle as directed under the seedcontainer of the Goldstein machine (Stewart, '34, plates 1 and 2). This required
that the end point of the first stage of filling be estimated.
b) Not having a Mollison brass cylinder and funnel, the
current apparatus of the laboratory was used for steps 8
and 9 ; it is the same as was used in 1934 (to the description
on p. 343 may be added the fact that the funnel has a slope
of 90").
I believe it will appear that neither of these alterations
have seriously impared the effectiveness of the test.
TESTING
The logical beginning for a test of this method is to fill a
series of standard skulls with mustard seed by the procedure
just outlined, in order to see how nearly a density of 767 gm./
1000 cc. is reproduced. The results of two such trials are
shown in table 1.
It will be seen that with the seed available in this laboratory I obtained an average density of 764 gm./1000 cc. in the
skulls by Breitinger's method of filling. The range is 756
to 774, or a difference of 18, which is greater than the 10
recorded by Breitinger for fifty-three trials on the same skull.
The cylinder also gives a variable density, owing chiefly to
the fact that readings were made to the nearest 5 cc.' Because
the cylinder-funnel combination gave a density greater than
that achieved in the skull (769: 764), the average for the
cylinder readings is lower than the true capacity of the series.
The most important conclusion to be derived from this is
that the mustard seed in this laboratory differs from that
nsed by Breitinger. I n support of this conclusion I may state
' 1393 would be read 1395; 1398 = 1400; 1397 = 1395, etc.
115
CRANIAL CAPACITY DETERMINATION
that subsequently I deliberately tried to create a greater
density of seed in the skulls by more vigorous shaking, more
forceful poking with the stick and thumb, and even by slapping
with the hand, but all to little effect.
I decided next to see how much effect size of seed had upon
the results. For the purpose of cleaning the seed this laboratory has long used a sieve made of galvanized wire, 16 mesh
TABLE 1
First results with the Breitinger method
TRIAL
SKULL
WAl'EB
NO.
I-
E-
gb
-. __I--
cc.
244080'
341791
244063
255051
225035
244055
244076
244074
244067
341794
Average
I
1345
cc.
I
1340
nm.
822
917
986
1023
1042
1049
1063
1077
1134
1166
1028
.-
O h
.-34
-"23
6%
.e
Clo
;b
~-
~
1065'
1195
1285
1330
1360
1365
1380
1400
1475
1075
1210
1290
1330
1365
1370
1390
1410
1475
-
-__
.e *
34
2 .E
-
TRIAL 2
I
nm./
000 CC.
772
767
767
769
766
768
770
769
769
765
768
Bm.1
1000
cc.
765
758
764
769
763
766
765
764
769
757
764
cc.
1065'
1190
1280
1330
1360
1365
1380
1420
1460
1530
-1340
-
gm.
820
915
984
1023
1047
1050
1064
1092
1122
1172
1029
-gm./
-0
.-xmd
5;
n
--
nm./
, 0 0 0 cc. 1000 cc.
770
769
769
769
770
769
771
769
768
766
769
763
756
763
769
767
766
765
774
761
761
764
l F o r a description of these standard skulls see Stewart, '34, p. 345.
Figures in this column rounded off to neareat 5 cc.
t o the inch. Few seed, even when broken, go through this
sieve, but all sand and dust are passed. By substituting a
sieve having 12 mesh to the inch,5 I was able to remove
quantities of small seed.s
' A 10-mesh copper screen was not as effective because the individual wires
were thicker.
'Each seed i s somewhat irregular in shape and may or may not pass through
the sieve according as different faces are presented. Hence, even after l011g
shaking some few seed continue to pass through the sieve.
116
T. D. STEWART
The next step was to adjust the cylinder-funnel combination
so as to get a seed density agreeing with that for the skull
given by the Breitinger method of filling. This is the reverse
of Breitinger's problem. Thus, a new series of trials were
run, using the larger seed and varying the funnel.' Instead
of the metal funnel previously used, which now gave a density
of about 775 gm./1000 cc., one made of cardboard was substituted. The new funnel differed from the old chiefly in
having a 60" slope and in lacking a spout (said not to affect
the flow of seed-Breitinger, p. 142). The round opening
was varied either by further cutting away the cardboard or
by applying adhesive tape. I n using this funnel the seed
were emptied into it all at once from a container which had
received them from the skull. The results of eight trials are
shown in table 2.
First of all it should be noted that the average cylinder
reading approaches the average water volume as the densities
in skull and cylinder likewise approach one another (principle
3). The best results were obtained in the final trials (7 and
8) where the average volumes are 2 cc. apart and the densities
only 1 unit apart. Examination of the individual readings
shows that in the last two trials the largest difference in
capacity was 11 cc. On the other hand, the density of seed
in the skull, the uniformity of which is the aim of the procedure, varied during eight trials on each of the ten different
skulls between 760 and 778, or 18 units. However, except for
two skulls (244080 and 225035) the greatest range in density
for any set of eight trials was 10 units ; the lowest range was
2 units for skull 244067. This would suggest that Breitinger's
findings, based for the most part on a s i n d e skull, a r e a little
too optimistic as regards general applicability.
' Variations in the height of the cylinder are not very effective in changing the
density of the seed. Varying the diameter of the cyliuder is of course out of the
question.
TABLE 2
ECght trials with the Breitinger method, w i n g large seed and varying the funnel opening
DENSITY
IN
CYLINDEB
SKULL
NO.
DENSITY
IN
SKULL
1. Fuunel oneuing = 2 1 mm.
om./
m./
--
ce .
1075
244080
1210
341791
1290
244063
1330
244051
1365
225035
1370
244055
1390
244076
1475
244067
1540
341794
2794461 -1605
Average 1365
1 0 0 0 ee.
1 0 0 0 ce.
765
771
773
774
772
774
772
772
772
765
771
761
768
7 70
776
774
771
765
770
7 74
-762769
>YLINDER
VOLUME
2 Same
-__fuunel as in 1
ec.
I
Same
Same
Same
Same
Same
Same
Same
Same
Same
Same
_
Same
Same
Same
Same
Same
Same ’ Same
Same 1 Same
Same
Same
Same
Same
Same 1 Same
Same I Same
Same
Same
Same i Same
~Average 1 Same
I
i
767
778
766
767
764
770
764
775
765
778
765
769
766
768
766
769
763
773
764.766
_
765
771
.~
n g = 2 1 mm.
1082
831
768
773
927
767
1208
766
990
760
1302
767
1025
759
1350
771
1054
763
1381
772
1059
765
1385
773
1064
765
1390
765
1135
766
1482
769
1193
1557
766
775
1608 -__
1232
766
768
764
770
ing -_
= 20 -mm.
iel
_ _opt .
__
826
770
768
1201
774
930
769
986
1289
765
764
768
1025
1335
771
1044
1360
768
765
1374
769
1056
771
768
1065
1387
766
769
1134
1474
769
769
1185
1540
769
1599
1230 - 769
766
___
-I. - 1363
I
1048
769
I
768
_ _
~
~
nm.
1 0 0 0 cc.
gm’/
774
829
772
932
774
998
1026
773
1056
772
1064 I
774
1063
772
1135
772
1184
769
1228
767
1052
772
1071
1208
1290
1328
1368
1375
1376
1471
1540
1601
1363
ing= 22 mm.
Same
Same
Same
Same
Same
Same
Same
Same
Same
~Same
Averaee
WEIGHT
O F SEED
1
771
770
774
771
774
I 777
765
769
iG9
765
570
I
1
4.
1085
1202
1300
1349
1380
1380
1391
1485
1560
1609
1374
921
993
1032
1055
1056
1067
1137
766
764
765
764
765
767
766
765
825
928
989
1022
1054
1052
1072
768
768
761
762
765
766
766
6
1074
1208
1300
1342
1378
1374
1399
1483
1553
1611
1372
-_
-
__
-
i72
761
770
776
773
771
768
771
775
-766
770
-
767
7G 7
767
i68
772
768
771
769
774
- 769
. 7G9
__
inelas ii - 8
Same
Same
769
1069
774
Same
766
760
Same
1199
919
Same
766
1290
Same
i66
988
Same
Same
1336
1025
767
i71
Same
769
Same
1365
769
1050
Same
Same
13i2
768
769
1054
Same
769
76.5
Same
1383
1064
Same
769
7G9
Same
1475
1134
Same
770
571
Same
1542
1187
Same
Same
766
1599
1229 I 769
-4verage
I
Same
1363
1 1048 1
7
6
9
1
’
i
G
S
.~. _ _
.
ISubstituted for 244074 which mas no longer available. It is the skull of a male Alaskan
Eskimo and has a cranial index of 75.3. Three trials 1vit.h water gave the following results:
1600, 1605, 1605 cc.
117
118
T. D. STEWART
DISCUSSION
This examination of the Breitinger method would seem to
be a severe test because it duplicates in a measure the circumstances under which any standard procedure must operate.
However, I believe the results of these trials will convince
almost every one that, with the minor changes indicated, this
method will yield satisfactory results even without personal
instruction.
One necessary modification involves the density of the seed.
Breitinger’s report implies, although he may not have intended it, that a density of 767 g m . / l O O O cc. should be adopted
as a part of the procedure. As here shown, it is not likely
that every laboratory will have the same quality of seed, and
therefore will not get this density figure. Lacking such
standard seed, it would be foolish to standardize the density.
The present results suggest, at least, that when the quality
of the seed varies, the density in skull and cylinder varies
equally. This remains to be proved definitely. However, if
true, the Mollison cylinder and funnel, used with the Breitinger technique, should give reliable results regardless of
seed quality.
Rather than standardize the apparatus I would suggest that
some such course as that followed in the present study be
recommended. This would permit the adaptation of existing
apparatus and avoid undue expense to the laboratories concerned. I n this coniiection there is something to be said in
favor of a cylinder both taller and narrower than that described by Mollison ; namely, the greater accuracy in reading.
Also, since a tall slender cylinder increases the density, this
can be compensated for by a larger funnel opening, which in
turn speeds the flow of the seed, thus saving time.
Turning to the details of the skull-filling procedure, I would
like to state some impressions not mentioned in connection
with the testing. I n the course of handling the standard
skulls during this study I came to feel that the variations from
true capacity were due in part to variations in skull morphology. F o r instance, in one skull the foramen magiium was
CRANIAL CAPACITY DETERMINATION
119
so small that the stick could not be introduced at much of a n
angle; in another the occipital region was so formed that
the last stage of filling progressed with unusual rapidity.
Thus perhaps the range of trial capacities for the individnal
standard skulls reflects somewhat the varying morphology
of these skulls. This is a good reason for making tests 011
more than one standard skull.
Again, at two stages in the procedure the directions were
not clear enough. It is stated that the initial filling should
continue until the skull is four-fifths full (p. 143). This point
is difficult to judge and I feel that it considerably influences
packing, at least in the extremes of skull size. Also, in connection with probing with the stick, the position of the skull is
not indicated. I believe that packing is more effective at
this stage if the skull is held with the frontal directed downward.
Thus far we have not been concerned with the last two
sections of Breitinger ' s paper ; these also deserve some coniment. After developing his method, Breitinger has sought
to demonstrate its efficiency by showing how accurately the
capacity of skulls of unknown volume can be determined.
Taking ten Melanesian and ten Bavarian skulls, he determines
their volume by this method and then also calculates the same
from the weight of the seed, using a density factor. Although
not stated, the density factor used in this calculation is presumably that which the method produces, namely, 767 p./
1000 cc. It is obvious that this figure is the same as that
given by the cylinder-funnel combination, and therefore it is
far from gratifying that the same volumes should result;
indeed it would be peculiar if they differed. That a particular
density of seed is obtained i n a skull of unknown capacity
can only be inferred from experience with standard skulls ;
it is not proved.
I would like also to discuss Breitinger 's statement (p. 146)
that the capacity of the second standard skull by his method
was the same before and after water-proofing; in other words,
that he failed to substantiate my finding of a change in capacity under these circumstances (Stewart, '34, pp. 348-351).
120
T. D. STEWART
It will be recalled that I was attempting to find out whether
the condition of the internal surface of the skull affected seed
packing. To this end I tested skulls of unknown volume by
two different methods before and after coating the interior
surfaces with paraffin. The main difference between the two
methods was in the degree of seed packing (density). One
method, which I designated ‘minimum packing,’ gave a density
of about 747 gm./lOOO cc. ; * whereas the other method, called
‘maximum packing,’ gave a density of about 798 gm./1000 cc.
Both methods were felt to be reliable for standard skulls
within a possible error of 15 cc. The demonstrated effect of
altered internal surface upon the results by the ‘maximum
packing’ method was so striking that it was presented for
what i t was worth. I have not been able to follow it up
further. That Breitinger’s result does not disprove my finding is due probably to the fact that the seed density produced
by his method (767 gm./lOOO cc.) is scarcely beyond the ‘minimum packing’ class, for which no variation in capacity due to
altered internal surface was claimed by me.
SUMMARY
1. Breitinger has reported a standard procedure for filling
the skull with mustard seed for which he claims uniform results, even in the hands of others who have been instructed
by him.
2. On the suggestion of Miss M. L. Tildesley of the ‘‘ComitCI
de standardization de la technique anthropologique’ ’ the
author has tested this method, using only the printed instructions and the available apparatus.
3. It was found that the density of the seed depends in part
upon their quality and therefore the density should not be
standardized.
4. Using a convenient seed density, results essentially comparable with those of Breitinger were obtained.
’A typographical error makes this 757 in the original, page 349.
CRANIAL CAPACITY D E T E R M I N A T I O N
121
5. The findings are discussed and four general principles
essential to the correct determination of cranial capacity are
emphasized.
LITERATURE CITED
BREITINGER,
EMIL 1936 Zur Messung der Schadelkapazitiit mit Senfkornern.
Anthrop. A m . , XIII, 140-148.
MOLLISON,
TR. 1932 Hohlraummessung und Volumenbestimnung. Anthrop.
Am., VIII, 290-294.
T. D. 1934 Cranial capacity studies. Am. J. Phys. Anthrop., XVIII,
STEWART,
33 7-361.
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