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Endocranial form of gorilla skulls. With special reference to the existence of dolichocephaly as a normal feature of certain primates

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ENDOCRANIAL FORM OF GORILLA SKULLS
WITHSPECIAL
REFERENCE
TO THE EXISTENCE
OF DOLICHOCEPHALY
AS A
NORMAL
FEATURE
OF CERTAIN
PRIMATES
H. A. HARRIS
Instgtute of Anatomy, University College, London; and
Washington University, Saint Louis
INTRODUCTORY REMARKS
The recent discovery of a fossilized skull at Taungs in South Africa
was an event of great importance. Professor Dart of the Witwatersrand
University (Johannesburg)-our erstwhile colleague at Saint Louis and
a t London-described the specimen as a member of an ancient group,
intermediate between living anthropoids and man, and gave it the name
of Australopithecus africanus. British anatomists, prominent among
them Sir Arthur Keith, Professor Elliot Smith and Professor Robinson,
heralded the importance of the discovery and differed considerably as
regards the true morphological significance thereof. Dart (1),in describing Australopithecus, says that “the whole cranium displays humanoid
rather than anthropoid lineaments. It is markedly doZichocephaZic and
Zeptoprosopic.”
Thus the longheadedness, together with the long
narrow face is regarded as a human attribute. Keith (2) lays great
stress on this character and says: “Even if it be admitted that the
Australopithecus is an anthropoid ape, it is a very remarkable one. It
is a true longheaded or dolichocephalic anthropoid-the first so f a r
known.” Robinson (3), obviously impressed by the dolichocephalic
character of the specimen is reported as follows : “The Taungs specimen
was the distorted skull of a chimpanzee just over four years old, probably a female.” Elliot Smith (4) in a lecture at University College said
“Even if it be admitted, which I am not prepared to do, that some
flattening of the brain case occurred after death, the absence of salient
eyebrow ridges, the smallness of the jaws, and especially the reduction
of the prominence of the snout, confirm the claim that, although Australopithecus is an ape nearly akin to the gorilla and chimpanzee, it
does reveal a definite though slight indication of that refinement of the
features which represents the early stage in the process of the assumption of distinctively human characters.”]
With characteristic relevance, Bolk ( 5 ) immediately published a description of a strange gorilla skull from the collection in the Anatomical
’For latest and original study of the specimen, with new measurements and conclusions, see HrdliEka (A.), The Taungs Ape. Am. J . Phys. Anthrop., 1925, VIII,
0ct.-Dec. No., 379-392.
AM. J. PHYS.ANTHROP..1926,Val. IX,No.2.
157
H. A. HARRIS
158
Museum of the University of Amsterdam. Out of fifty skulls, this one
alone displayed marked dolichocephaly and leptoprosopy. The description of this single specimen of a longheaded anthropoid was particularly
suggestive, in view of the previous controversy as to the value of dolichocephaly in classifying the Taungs skull. At this time, in company
with Mr. J. Thornton Carter, I had the privilege of visiting the Natural
History Museum of Lord Rothschild at Tring Park. The whole problem
of the value of external and craniometric characters in determining the
range of variation on the one hand, and in determining the classification
of species on the other, has been discussed by Lord Rothschild (6). In
particular the variations in craniometric characters were so lucidly and
convincingly put forward by him that, a t his instigation, facilities were
made for the staff of the Institute of Anatomy to make a survey of the
anthropoids in the Rothschild collection. The collection of gorilla
skulls was moved to the Institute of Anatomy, and under the guidance
of Professor Elliot Smith, a survey was commenced.
MATERIAL AND METHODS
The material consists of 45 gorilla skeletons from the Rothschild
Collection, numbered in series from A. D. 1 to A. D. 45, of which 12 are
female and 33 male; with these are considered four skulls of the Anatomical Museum of University College, of which C. A. l , 2 and 4 are
male, and C. A. 5 is female. Thus the total represents 49 skulls, 36
male and 13 female. The only skull which is not completely adult is
that of a young male, A. D. 2, in which the third molars have not
erupted and the occipital and sagittal crests are not well developed.
(A)
CRANIAL CAPACITY
Wingate Todd (7) says that "there is no method of obtaining cranial
capacity with absolute accuracy and there is no method of approximation which is not open to serious objection." His learned analyses of
the various methods described by Martin, Pearson, Macdonnell and
HrdliEka and the severe checking of his own methods show that the
error may amount to 3%. In view of this fact the white mustard seed
method (HrdliEka) was employed, filling the skull by Flower's method
and emptying the seed into a 1000 ccs. cylinder by means of a large
funnel the stem of which was cut short, the bore at the exit being 2 cms.
Each reading was repeated five times and the average was regarded as
the cranial capacity.
(B)
FACIAL INDEX
The facial index is usually measured in terms of the ratio of the nasoalveolar distance to the maximum bizygomatic width. This method
ENDOCRANIAL FORM OF GORILLA SKULLS
159
was extensively employed as the “upper facial index of Kollmann.”
It is unsuitable for anthropoids as the nasion is not easily determined
owing to the variable development of the supraorbital crest and the
early union of the nasals and frontal a t the fronto-nasal suture. Accordingly, the method of Bolk was pursued. The greatest breadth is
measured between the right and left points at which the zygomatic
arch bends itself round into the lateral orbital margin. The greatest
length is measured in profile from the highest point in the mid-line of
the crista supraorbitalis to the anterior margin of the premaxilla between the central incisors. The ratio of this breadth to the length,
multiplied by one hundred, will be referred to as the Facial Index of
Bolk. Where the Facial Index of Bolk is 100 or more, the face is classed
as chamaeprosopic or broad and where the index is less than 100, the
face is classed as leptoprosopic or long. The method of taking the
measurements is depicted by the arrows in Fig. I (A) to (D), which is
after Bolk (op. cit.).
(C)
CEPHALIC INDEX.
THE RADIOGRAPHIC METHOD
No satisfactory craniometric method for the skulls of anthropoids
has yet been obtained. The only method which would permit of true
comparison with man would necessitate the comparison of endocranial
dimensions. This necessitates section of the skull in the mid-line, an
act which destroys a band of bone from 1.5 to 2 mms. thick as a result
of the spread of the teeth of the saw. All external measurements of
length in the anthropoid skull are vitiated by the strongly developed
crista occipitalis and, in the gorilla, the more strongly developed crista
supraorbitalis. A fact which has not been so clearly recognized is the
still greater error in determining the breadth of the brain case. The
parietal eminences of the anthropoids are not well developed : they do
not overlie the point of maximum breadth: the mastoid air sinuses in
the male gorilla extend into the squama of the temporal bone superior
and even anterior to the external auditory meatus and may invade the
lower margin of the parietal bone by transgressing the squamo-parietal
suture and so reach even to the parietal eminence. The point of maximum breadth sometimes lies as much as 4 cms. anterior to the external
auditory meatus.
Keith (8) says: “The present manner of description by angles and
indices is a method that leads only to the accumulation of a mass of
most useless, cumbersome material. The describers seem to have lost
all sight of the skull as a functional organ, with its form adapted for
its two main uses, as a brain cover and a tooth carrier.” Bolk (loc. cit.)
FIG.1.-After
B
D
Bolk. The arrows indicate the method of measuring the facial length and breadth in the short-faced (A)
and (c) and long-faced skulls (B) and (D).
P
P
ENDOCRANIAL FORM OF GORILLA SKULLS
161
says that in studying the gorilla, “the terms dolichocephalic and brachycephalic are not truly applicable in that the index cephalicus is not
taken in the same way from the full grown Gorilla as from man. Keith
(Q), in his determination of the average length of 10 gorilla skulls, excluded from the length the prominences due to the frontal air sinuses
and the external occipital protuberance. But he measured the breadth
from one parietal eminence to the other. Such a measurement of breadth
is open to question, as the parietal eminence may be obscured in the
adult male gorilla by the great development of the air sinuses, and the
point of maximum endocranial breadth may lie as much as 4 cns.
anterior to the external auditory meatus a t a considerable distance from
the poorly developed parietal eminence.
Bolk accordingly obtained what he calls an Index Encephalicus for
the length-breadth relation of the cranial cavity. He made a sagittal
section of the skull and obtained the length and breadth therefrom. The
Fronton of Bolk is the point where the frontal wall and the base of the
skull meet anteriorlyinthe middle-line. The Occipiton is the point on
the occipital surface of the endocranial wall furthest from the Fronton.
This is the greatest length of the cranial cavity. The greatest breadth
is found by adding together the greatest depth of the cranial cavity of
the right and left halves. This is a troublesome method, as in the first
place a band of bone is destroyed by the act of sawing, and secondly the
maximum breadth of each half has to be determined by a laborious
method of trial over a considerable area by means of a depth gauge or
other comparable arrangement.
Accordingly a new method was devised for the breadthlength relation
of the skull. The largest gorilla skull is mounted upside down in the
Frankfort plane, with cylindrical metal pointers in the right and left
external auditory meatus and a third pointer supporting a t its tip the
left infraorbital margin. The third pointer is not quite in the same
horizontal plane as the other two but lies a t a distance of 2 mms. below,
so as to have its sharp tip a t the same level as the lower margin of the
two cylindrical pointers which are thrust in to the right and left external
auditory meatus. By this manoeuvre it is possible to maintain the true
superior margin of the left and right external auditory meatus a t the
same level as the left infraorbital margin, so guaranteeing that the skull
is in the Frankfurt Plane. The level of these pointers is maintained
constant, but the stands supporting them can be moved to and fro on
the horizontal table. The largest male skull is mounted in this manner
so that the sagittal crest just clears the table.
162
H. A. HARRIS
A radiographic filmis placed on the horizontal table beneath the skull;
another film is mounted in a vertical plane parallel to the sagittal plane
of the skull at such a distance that the distance from the Frankfurt
plane to the horizontal film on the table is equal to the distance from
the sagittal axis of the skull to the vertical film. Two X-ray tubes are
mounted so that the upper tube is centered over the basion which is
marked by a small arrowhead of lead foil, and the lateral one is centred
over the external auditory meatus. The tube distance from the film in
each case is constant so that the radiograms of the norma verticalis and
norma lateralis are of equal magnification. Lateral and vertical radiograms of all the skulls were thus taken, so that two series of radiograms
were obtained of constant and equal magnification.
Two of the skulls, C. A. 1 and C. A. 4 were now sectioned in the
sagittal plane by a thin band saw. The actual maximum length and
breadth was determined after the method of Bolk. Furthermore, lateral
radiograms of the half skull were taken by placing the half skull with
its sagittally sectioned surface in contact with the film,so that the
magnification of the image was unity. Thus three standards are obtained for determining the magnification of distances in the Frankfurt
plane and in the sagittal plane on the two series of radiograms. The
magnification can be calculated :
(1) By actual measurement in terms of the distance of the Frankfurt plane and sagittal plane respectively from the x-ray tube
and from the photographic film.
(2) By actual measurement of the two sectioned skulls.
(3) By actual measurement on the radiograms of the half skulls of
C. A. 1 and C. A. 4 in which the sagittal surface is in contact
with the photographic film.
All three methods showed the magnification of the radiograms to be
approximately 1.1. Thus distances in the two standard planes can be
reduced to actual distances by dividing such distances on the radiogram
by the common magnification factor of 1.1.
It is important to stress the fact that this magnification factor can
only be employed for distances which lie in the Frankfurt plane or in
the sagittal plane in the radiograms of the nonna verticalis and norma
lateralis respectively. First of all consider the problem of the maximum
breadth of the skull. In Fig. 2 the Frankfurt plane is F P and the plane
of the image on the photographic film is I M. The magnification of all
distances in the plane F P on the image I M is 1.1. But the actual
maximum breadth of the skull lies in some position such as B H and the
FIG,2. Gorilla skull in position to show magnification of
maximum breadth BH at BIH' in the plane of the film
irnaEe IM. FP is the Frankfurt plane.
FIG. 3. Brachycephalic Gorilla skull in posiiton to
show magnificationof maximum length LH at L W in
the alane of the film image IM. FP is the Frankfurt
H. A. HARRIS
16#
magnification of this line on the plane of the image I M will be less than
1.1, in proportion as B H recedes from F P and approaches I M. The
actual apparent maximum endocranial breadth on the radiogram was
measured and divided by 1.1. This gives a reading for the actual
breadth which is too small, as the magnification of B H on an average
is in the neighbourhood of 1.07 to 1.08. The apparent maximum breadth
was measured on the series of radiograms of the norma verticalis and in
each case this dimension was divided by 1.1, so giving a series of values
for the breadth of the skull which were uniformly high.
As regards the maximum length of the skull, in addition to the factor
considered above for breadth, there is another factor due to the obliquity
between the actual line of maximum length and the Frankfurt plane.
In Fig. 3, F Pis the Frankfurt plane, I M is the plane of the image and
L H is the actual maximum length in the sagittal plane. The magnification of all distances in the plane F P on the image I M is 1.1. The
magnification of L H in the plane I M is less than 1.1, according as L H
recedes from F P and ranges between 1.08 and 1.09. Moreover the
projection of L H on the plane I M is decreased proportionally to the
angle of obliquity of L H to F P. In the case of a longheaded skull
(Fig. 4) this obliquity is usually less than 10" and in the case of a broad
headed skull the obliquity is almost nil. The obliquity of L H to F P
and to I M will thus cause the length to be shortened on the image by
a factor ranging from cosine 10" to cosine 0" i.e. from 0.98 to 1.00. Accordingly, in view of the relative insignificance of this small obliquity,
the apparent maximum length as measured on the series of radiograms
of the norma verticalis has been divided in each case by the standard
factor of magnification 1.1, in order to obtain the endocranial length of
the skulls.
Both length and breadth have thus been calculated by dividing the
maximum length and breadth on the series of radiograms of the norma
verticalis by 1.1 and the index is called the "Radiographic Encephalic
Index." The errors of the method due to the position of the lines of
maximum length and breadth have been shown to be within 27,. It is
hoped by further development of this technique to obtain an absolute
measurement for the actual maximum endocranial length and breadth.
(D)
EXOCRANIAL CEPHALIC INDEX
For the purposes of comparison a series of measurements were made
on the external aspect of the skulls, the length being measured ad
maximum from the external occipital protuberance to the supraorbital crest, and the width from the upper margin of one external
166
ENDOCRANIAL FORM OF GORILLA SKULLS
auditory meatus to that of the other. This is called the “Exocranial
Cephalic Index.” Such an index wiII show a very wide range because
of the marked variation in the development of the crests and air sinuses
of the skull.
GORILLA
SKULLS
OF ROTHSCHILD
COLLECTION
No.
Sex
13
2
4
A. D. 2
A. D. 14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
C.A.
44
45
C. A. 5 9
A. D. 1
3
4
5
6
7
8
9
10
11
12
13
Cranial
capacity
In ccs.
560
652
510
490
550
560
547
460
500
495
460
470
?
490
?
510
?
?
?
?
?
550
?
580
440
465
480
?
520
?
560
455
?
?
480
?
475
460
415
450
425
430
?
420
450
442
457
?
440
Facial index
of Bolk
110.9
129.2
111.0
100.7
113.7
97.5
111.6
111.3
100.0
111.8
112.5
109.1
113.6
113.5
120.8
108.9
110.3
113.6
101.4
110.4
97.7
96.3
114.4
113.6
111.1
108.1
104.1
106.1
97.9
92.9
125.3
105.0
97.5
96.8
110.5
?
108.7
96.2
110.6
114.0
110.4
110.9
106.5
102.4
106.0
98.5
110.9
107.5
105.8
“Radiographic” “Exocranial”
Encephalic index, cephalic index
endocranial index
84.7
80.5
84.7
85.8
74.4
78.2
76.9
80.3
80.3
80.8
76.8
77.2
75.2
73-2
76.6
72.1
77.2
81.1
77.2
79.7
79.2
78.7
74.0
74.4
76.6
74.2
79.5
80.1
76.0
76.0
72.7
82.5
81.4
77.2
74.2
75.0
82.6
85.2
80.0
78.3
79.1
84.2
84.8
86.8
82.8
84.9
82.8
79.7
80.7
87.2
70.9
84.7
78.8
67.6
74.6
78.5
73.9
72.6
66.5
77.3
77.5
78.6
70.1
78.0
72.9
83.0
76.4
75.1
70.4
65.6
66.7
69.3
78.2
68.4
77.8
68.6
84.7
75.6
67.0
72.4
64.9
76.0
76.9
60.4
82.9
79.4
77.1
75.5
75.5
76.4
77.1
75.1
79.5
76.8
76.5
?
81.0
Locality
Gaboon
Gaboon
French Congo
French Congo
Cameroons
Gaboon
S. Cameroons
S. Cameroons
Nguni River
Nguni River
Cameroons
Gaboon
French Congo
Cameroons
Cameroons
Cameroons
S . Cameroons
Gaboon
Cameroons
Bonila R.
Gaboon
Nguni River
Gaboon
Cameioons
Gaboon
Bonila R.
French Congo
Gaboon
Gaboon
Cameroons
H. A. HARRIS
166
(A) CRANIAL
CAPACITY
Collection
Rothschild
(H. A. H.)
Total No.
of skulls
34
23
11
29
5
27
7
Bolk(5)
Martin(l0)
Hr&Eka( 11)
Keith(l2)
39
27
12
?
?
7
?
13
7
T*
M. & F.
M.
F.
Chamaeprosopic
M. & F.
Leptoprosopic
M. & F.
Brachycephalic
(Radio. endocranial)
M. & F.
Dolichocephalic
(Radio. endocranial)
M.
M. & F.
M.
F.
M.
F.
M.
F.
M.
F.
AVWW
Max.
Min.
490ccs.
513
442
487
652ccs.
652
475
652
415ccs.
440
415
415
506
560
442
482
652
415
519
580
465
528
550
478
508
435
?
?
497
450
655
655
595
585
550
390
450
390
623
580
573
496
420
370
420
370
425
393
Notes:-The
greater the number of gorillas examined, the greater
does the average cranial capacity tend to become. Whereas Keith
gives the average capacity as 470 ccs. with a maximum of 620 ccs.
Hagedoorn (13) says that this average is far too small as it is already
surpassed by that of certain female skulls. The Rothschild skulls give
an average of 490 ccs. for both sexes; 512 ccs. for the male and 442 ccs.
for the female. This is not as large as the average given by Bolk i.e.
528 ccs. for both sexes, 550 ccs. for males and 478 ccs. for females. HrdliEka discusses the ratio of the female cranial capacity to the male
capacity as an index in terms of 100, and quotes Oppenheim (14) to the
effect that the value is 85. Bolk’s figures give a value of 86.9, Keith’s
90.5, and the present collection 86.3, a value which is very close to
that of Bolk.
The average cranial capacity of the nine leptoprosopic skulls is 506,
with a range from 442 to 560 ccs. The average of the eight dolichocephalic (radiographically) skulls is 519, ranging from 465 to 580 ccs.
Bolk’s single specimen falls within these limits with a capacity of 550 ccs.
ENDOCRANIAL FORM OF GORILLA SKULLS
167
(B). FACIAL
INDEX
OF BOLK.
Collection
Rothschild
(H. A. H.)
Total No.
of skull6
48
35
13
39
9
28
7
11
Max.
Mis.
107.9
108.3
106.8
110.4
129.2
129.2
114.0
129.2
92.9
92.99
96.2
100.0
96.8
98.5
92.9
Chamaepros
M.
- -.
Leptopros.
111.1
129.2
100.0
96.7
97.9
92.9
Chamaepros.
108.5
114.0
102.4
97.3
98.5
96.2
111.5
122.6
103.4
Type
Average
M.& F.
M.
F.
Chamaepros.
M. & F.
Leptopros.
M. & F.
M.
F.
2
Bolk
49
1
Leptopros.
F.
Chamaepros.
M. & F.
Leptopros.
89.5
M.
I
H'
FIG.4. Dolichocephalicgorilla skull in position to show magnification
of maximum length LH at LlH' in the plane of the film image IM.
The maximum length LH makes an angle with the FP and IM.
H. A. HARRIS
168
Notes:-Leptoprosopy
characterizes nine of the gorillas examined.
The average value of the facial index in the nine leptoprosopic skulls is
96.8, ranging from 98.5 to 92.9. Not one of the skulls was so markedly
leptoprosopic as Bob’s sole specimen which had a value of 89.5. Of
the chamaeprosopic skulls 15 range from 100 to 1U9.9, 21 range from
110 to 119.9 and three have values above 120. The most markedly
chamaeprosopic skull, (C. A. 2 ) is also that male skull which has the
largest cranial capacity, with marked development of the crests and
air sinuses. Two of the female skulls are leptoprosopic.
(C).
RADIOGRAPHIC
ENDOCRANIAL
INDEX,
OR ENCEPHALIC
INDEX.
Collection
Rothschild
(H. A. H.)
Total No.
of skulls
49
36
13
41
8
40
9
Bolk
Keith
Keith (2)
HrdliEka(l6)
10
?
1
1
M.& F.
M.
F.
Brachyceph.
Dolichoceph.
Chamaepros.
Leptopros.
Brachyceph.
Brachyceph.
Taungs Skull
Taungs Skull
Average
Max.
Min.
79.1
77.9
82.4
80.2
73.6
79.0
79.6
86.8
85.8
86.8
86.8
74.4
86.8
85.2
85.9
80.0
71.0
74.0
?
72.I
72.1
78.3
75.0
72.1
72.1
76.0
80.6
?
?
Discussion:-The
radiographic method of estimating the endocranial index shows that eight of the skulls are dolichocephalic. On
the average, the male skulls display a much wider range of variation
than the female. The female skulls range from 78.3 to 86.8 with an
average of 82.4, whereas the male range from 72.1 to 85.8 with an
average of 77.9. Thus the dolichocephalic character is more marked
in the male, in terms of endocranial measurement. All eight dolichocephalic skulls were male. The thirteen female skulls were consistently
brachycephalic. This brachycephalic character of the female gorilla
skull is comparable to what is found in the female human slcull. Yet,
two of the female skulls are leptoprosopic.
The average endocranial index of the chamaeprosopic and leptoprosopic groups are very close together, 79 and 79.6 respectively. Although Bolk’s specimen was both leptoprosopic and dolichocephalic, it
should be noted that there is no close correlation between the leptoprosopic and dolichocephalic characters in members of the Rothschild
series. Not one of the nine leptoprosopic skulls is dolichocephalic as
they have endocranial indices which range from 76 to 85.2, With an
average of 79.6. Conversely, not one of the eight dolichocephalic skulls
is leptoprosopic, the eight dolichocephalic skulls having facial indices
which range from 108.1 to 125.3 with an average of 113.5. Hrdli&a
ENDOCRANIAL FORM OF GORILLA SKULLS
169
(15), in a comparison of the facial with the cephalic index in a series of
orang skulls, pointed out the lack of correspondence between these two
indices, and suggested that “the facial growth is apparently controlled,
unlike in man, much more by the development of the teeth and facial
muscles than by that of the cranial vault.”
The absence of close correspondence between the facial indices and
endocranial indices in the gorilla demonstrates that the development of
the skull and the development of the face cannot be too closely related
in terms of “brain cover” and “tooth carrier.’’
The preliminary estimates of the cephalic index of Australopithecus
have varied from 71 by Keith (2) to 74 by HrdliEka (16). These figures
lie between the limits of the dolichocephalic gorillas of the Rothschild
Collection and between the h i t s of dolichocephalic man. Too much
importance should not be attached to the cephalic index in interpreting
a given anthropoid or human specimen. Bunak (17), in a recent study
of the lambdoid and sagittal crests of anthropoids has shown that there
is a close, but not a full correspondence between the extent of the temporal muscles, the size of the canines and the development of the lower
jaw. There is, apart from these factors, what he calls a “crest factor”
which is a systemic character of certain species and sub-species of
Primates. It is this same “crest factor” which Lord Rothschild has
employed in the separation of the species and sub-species of gorilla.
Similarly with regard to supra-orbital crests, the facts have been clearly
stated by Elliot Smith (18) : “The development of the eye-brow ridges
is not of much importance as an index of race. It is neither an exclusively
primitive character nor a distinction of higher race. It is found developed in Pithecanthropus, Rhodesian Man, Neanderthal Man, and in
the Australian and Alpine Races, whereas a defective development of
the ridge is characteristic of Eoanthropus, the Negro, the Mongol and
the Mediterranean Races, while the Nordic Race occupies a position
between the two.”
As for the skull crests so for endocranial skull form; there is not only
a “muscle” factor, a “dentition” factor a “face” factor and a “brain”
factor, but there is also a “skull” factor which is at present too complex
to be analysed in terms of race alone.
In Fig (5) are shown the radiograms of the norma verticalis of seven
of the gorilla skulls selected a t random on the basis of the differences
in skull form pointed out by Lord Rothschild. The range of the endocranial or encephalic index obtained by the radiographic method is
from 72.1 t o 86.8, the upper row being brachycephalic; and the lower
row dolichocephalic.
TOPROW. A. D. 40=72.7. A. D. I4=74.4. A. D.25=72.1.
Botlom Row. A. D.2=80.5 A. D. I =85.2. A. D. 8=86.8. A. D. 26=76.6.
ences in skull form described by Lord Rothschild. The endocranial cephalic indices are:-
FIG.5. Radiograms of the norma verticalis of seven gorilla skulls selected at random by sight to show differ-
ENDOCRANIAL FORM OF GORILLA SKULLS
171
(D). EXOCBANIAL
CEPHALIC
INDEX.
Collection
Rothschild
(H.A. H.)
Total No.
of skulls
48
36
12
30
18
Average
Max.
Min.
M.& F.
M.
F.
74.9
73.9
77.7
87.2
87.2
82.9
60.4
60.4
75.1
Brachyceph.
(exocranial)
Dolichocmh.
(exocraHa1)
78.3
87.2
60.4
69.2
74.6
60.4
Type
The wide variation in the exocranial cephalic index is due to the great
variation in the development of the crests and air sinuses in the male
skull. Here again the female shows but a small degree of variation,
with a range from 75.1 to 82.9 and an average of 77.7 whereas the male
ranges from 60.4 to 87.2 with an average of 74.9.
SUMMARY
1. A method is devised for rapidly obtaining by radiographic means
a breadth-length ratio for the endocranial aspect of the intact skull.
2. Dolichocephaly is demonstrated in eight gorilla skulls in a series
of 49 and Ieptoprosopy is also demonstrated in nine of the skulls. In
no case was a given skull both leptoprosopic and dolichocephalic, so
that the correlation between skull form and face form is not very marked
within the series.
3. Dolichocephaly, per se, cannot be employed as a character of any
importance in deciding whether a given fossil skull possesses humanoid
characters.
4. The range of cephalic index in this series is comparable to the
range shown by man, from 72 to 87, both in the New World and the Old.
CONCLUDING REMARKS
Further attempts are being made to devise a speedy method of obtaining the maximum endocranial length and breadth of the skulls of
anthropoids by means of the use of the fluoroscopic screen and internal
callipers. Our thanks are due to Lord Rothschild for placing this unique
collection of gorilla skulls at our disposal and it is proposed t o study the
question of geographical distribution of species and sub-species when an
opportunity is found to examine the records concerning location of the
specimens in detail. Mr. Melville and Mr. Farey, technical assistants
a t University College, have devoted much time and thought to the perfecting of the method. My colleagues at Washington University have
also been most ready to assist.
1’7e
H. A. HARRIS
LITERATURE
Dart, R. A. Australopithecus Africanus: The Man Ape of South Africa.
Nature, Feb. 7 , 1925, 195-199.
Keith, Sir Arthur. The Fossil Anthropoid Ape from Taungs. Nature,
Feb. 14, 1925, 234.
Robinson, A. The Taungs Skull. Br. M d . J., March 25, 1925, 622.
Elliot Smith, G. Lecture delivered at University College, London, May 22,
1925, and I l l w t r a k d London News, Feb. 14, 1925.
Bolk, L. “On the existence of a dolichocephalic race of Gorilla.” Kon. AR.
Wet. Amsterdam, 1925, XXVIII, 204-213.
Rothschild, Lord. Notes on Anthropoid Apes. Proc. ZooE. SOC.LOW‘.,1904,
413440.
Further Notes on Anthropoid Apes. Proc. ZooE. SOG.Lond.,
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Todd, Wingate & Kuenzel, W. The Estimation of Cranial Capacity. A m . J .
Phys. A t ~ t l r ~ p1925,
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Keith, A. An Introduction to the Study of the Anthropoid Apes. Natural
Science Reprints, London, 1897, 5.
Keith. A. On the ChimDanzees and their relationship to the Gorilla. Proc.
Zoob. Soc. London, Makh 7, 1899, 311.
Martin, R. Lehrbuch der Anthropologie. Jena. 1914, 652.
HrdliEka, A. Weight of the Brain and of the Internal Organs in American
Monkeys, with data on Brain Weight in other Apes. Am. J . Phys. Anthrop.
1925, VIII, 201-226.
Keith, A. The Growth of Brain in Men and Monkeys. J. A m t . Er Phys.,
1895, XXIX, 282-301.
Hagedoorn, A. Schadelcapaciteit van Anthropomorphen. Ned. Tijdschr. v.
Geneesek., 1923.
Oppenheim. Zur Typologie der Primaten Craniums. 2.Morph. 6 Anthrop.,
1911, xrv.
HrdliEka, A. Anatomical Observations on a Collection of Orang Skulls from
Western Borneo: with a Bibliography. Proc. U. S, Nat. Mas., 1906,
XXXI, 539-568.
HrdliEka, A. The Taung’s Ape. Am. J. Phys. Anthrop., 1925, VIII, 379-392.
Bunak, V. The Crest on the Skulls of Primates. Russ. Anthrop. J. MOSCOW,
1923, XII; also Anthroropologie (Prague), 1924, 11, 131-134.
Elliot Smith, G. Essays on the Evolution of Man. So, Oxford Univ. Press,
1924, 11.
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