Three-dimensional imaging and osteometry of adult human skulls using helical computed tomography.

To make a digital image database of human craniology, we optimized the three-dimensional (3-D) images of 29 dried human skull specimens by helical computed tomography (CT). For the verification of the quantitative exactitude of these image data, we manually measured nine items of direct distances between standard anthropologic points on each skull and the corresponding distances projected on the CT monitor by specifying the respective points. The results obtained by the two methods of manual and CT measurements were compared and statistically analyzed. The CT measurements were so exact that the lower limit of correlation coefficients (95% of the confidence interval) between the two results was more than 0.8 in six items; i.e., maximal cranial length and breadth, minimal frontal breadth, bizygomatic breadth, distance between ectomolares and nasion-basion length. In contrast, the CT results were less well correlated with the manual measurements of three items; i.e., distance between bilateral mastoidales, total facial height, and nasal breadth. We concluded that the qualitative representation of 3-D CT images was adequate, although some quantitative data may be incorrect. The inaccuracy is suspected to be due to the difficulty in specifying the standard points on the CT images, and due to the differences in measurement procedures between the direct and projected distances.

[Morphological studies on lower margins of nasal aperture in the skull of Hokkaido Japanese].

It is well-known that the lower margins of nasal aperture in the human skull may be classified into the following four types, i.e., Forma anthropina, Forma infantilis, Fossae praenasales and Clivus nasoalveolaris, and that the rates of appearance of these four types differ with races. In the present study we made morphological studies on the lower margins of nasal aperture of 465 Hokkaido Japanese skulls, 463 skulls with symmetrical nasal aperture and 2 skulls with asymmetrical one, and compared the findings with those of all races in the world, especially of the Japanese, Ainu, Moyoro Man, Hamanaka Site Man and Eskimo. Forma anthropina was found in 330 skulls (71.27 +/- 2.10%) among the 463, marking the highest rate. Forma infantilis, found in 74 skulls (15.98 +/- 1.70%) among the 463, marked the second highest rate. Fossae praenasales, found in 42 skulls (9.07 +/- 1.33%) among the 463, marked the third highest rate. These 42 cases of Fossae praenasales were further classified into three types, i.e., sub-Forma infantilis, 17 (40.48%), typical Fossae prenasales, 23 (54.76%) and sub-Clivus nasoalveolaris, 2 (4.76%). Clivus nasoalveolaris, found in 17 skulls (3.67 +/- 0.87%) among the 463, marked the lowest rate. As a whole, the rates of the four types in the Hokkaido Japanese were close to those in the other groups of the Japanese in Kinai and Hokkaido (Ito).

[Studies on the foramen vesalius in the Japanese juvenile and adult skulls].

Foramen Vesalius is known to be an inconstant foramen, which appears in the anteriomedial side of the foramen ovale. The foramen Vesalius is classified into the open type and the closed type. We studied the frequencies and the types of foramen Vesalius in Japanese by examining 20 juvenile skulls from 3 months to 8 years old and 400 adult skulls from 18 to 91 years old. Of the 20 juvenile skulls, 11 skulls (55.00%) had foramen Vesalius. Of the 400 adult skulls, 87 skulls (21.75%) had foramen Vesalius; 69 (21.50%) in 321 male and 18 (22.78%) in 79 female skulls. No remarkable differences were observed in the ratio between the male and the female, and between the left side and the right side. Among the 69 adult male skulls, the foramen Vesalius was bilateral in 52 skulls (75.36%) and unilateral in 17 (24.64%); among the 18 adult female skulls, it was bilateral in 13 (72.22%) and unilateral in 5 (27.78%). The ratio of the closed type was slightly higher than that of the open type in both sexes and in both sides; however, no remarkable differences were observed. The skulls with one foramen Vesalius were most frequent; those with two followed it and those with 3 foramen Vesalius were least frequent. No remarkable differences were observed in the number of foramen Vesalius between the sexes and the sides.

Sex differences in the shapes of several parts of the young Japanese face.

For the purpose of studying the sex differences of the human face we collected five separate images, which consist of several parts of the face, from frontal view photographs of 48 male and 52 female college students. We traced outlines of their faces with simple lines (traced items), and made reproductions of the photographs of their eyes, mouth and nose by using a copying machine (reproduced items). The test subjects were 16 males and 8 females. They looked at parts of the face shown in each image, and categorized them individually by judging on their sex. Then, we calculated the percentages of correct judgments (percentage correct) for each image. By comparing the percentage correct between male and female we concluded that the sex of the subjects did not affect the results of their judgments. In the traced items the percentage correct for the face as a whole, which contained the outlines of the eyes, mouth, nose and the lower jaw, was 69%, but it decreased to 61% when the outline of the lower jaw was removed. Hence, the outline of the lower jaw apparently has a characteristic shape easily noticed by males. In the reproduced items the percentage correct was 65% for the eyes, 68% for the mouth and 58% for the nose. The mouth, therefore, has more distinguishing characteristics than the eyes or nose, especially with females. On the other hand, there is no correlation between the percentage correct for the eye, mouth and nose items. Hence, we concluded that the sexual specificity for the shape of the young Japanese face appears on their parts independently.

The fusion of ossification centres in the cartilaginous and membranous parts of the occipital squama in human fetuses.

The process of fusion of the ossification centres in the occipital squama is described in human fetal skulls. During the 3rd fetal month, irregular ossification centres appear in the membranous tissue behind the cartilaginous supraoccipital bone plate. The centres rapidly develop to form a meshwork of bony trabeculae which cover the external surface of the supraoccipital plate and then fuse with the primary interparietal part along its lateral edges. In the 4th fetal month, similar irregular ossification centres appear on the internal surface of the supraoccipital plate. After the 5th month, these ossification centres fuse with the root of the secondary interparietal part in the midline. They occasionally fuse with the lateral portion of the primary interparietal part in the early 5th month. These show that the external and internal surfaces of the supraoccipital part are covered with a thin sheet of bone ossified in membrane, which is periosteal ossification, while the main portion of this part develops in cartilage.

Developmental studies on the interparietal part of the human occipital squama.

The development of ossification centres in the membranous occipital squama is described, based on observations on human fetal skulls. The interparietal part develops basically from 3 pairs, 1 primary pair and 2 secondary pairs; an additional 4th pair is occasionally observed. The so-called separated interparietal bones (Inca bones) are formed by a failure of fusion between the primary and secondary centres, not between the supraoccipital and interparietal parts. The preinterparietal bones, which are developed from the additional 4th pair of interparietal ossification centres, are clearly differentiated from other anomalies in the lambda region by the shape of their territory and by their location. The issue still remains as to how to establish their identity in skulls from individuals of advanced age.

[Pterion and epipteric bones in Japanese adults and fetuses, with special reference to their formation and variations].

The formation and variations of the pterion and epipteric bones were examined in total of 614 Japanese skulls. The materials used consisted of 258 skulls of Japanese fetuses ranging from the fourth to the ninth month, 20 skulls of Japanese juveniles from the third month to 17 years of age, and 336 skulls of Japanese adults from 20 to 89 years of age. For the skulls examined the incidence of ossification in the fetal sphenoidal fontanelle was 3.6% on each side, whereas epipteric bones were observed in more than 10% of the juvenile and adult pteria. Great variation was seen in the form of the adult pterion. The most common form was a sphenoparietal contact in which the pteria were classified into usual (306 pteria), high (119), low (21), and narrow (32) types Another form of this type, a frontal process of the temporal bone without contact with frontal bone, was found in five pteria. The form of frontotemporal contact is classified into two types: One is with a frontal process of the temporal bone (17 pteria), and another is a K-shaped contact referred to as "stellate" (four). The two types were observable in adult skulls of all ages, although the fused pteria and fusing epipteric bones were most often seen in cases over 40 years of age. The results suggest that the pterion formation has two phases, the first occurring before the occlusion of sphenoidal fontanelle, and the second starting after 40 years of age.