On Some Morphological Characters of Japanese Lower Limb Bones from the View-Point of Squatting and other Sitting Postures in Jomon, Edo and Modern Periods

Abstract

This paper deals with five morphological characteristics of Japanese lower limb bones, which were considered to be influenced by squatting and other sitting postures. Material used are following Japanese populations from different periods; Jomon (stone age) Edo (17c-19c) and recent.Cervical fossa of ALLEN may be the complex characteristics due to various motion and posture which make antero-posterior surface of femoral neck press upon posterior margin of acetabulum. Frequencies of occurrence of this character are about 85% in the populations of Jomon and recent periods, nearly the same as in European white, and 100% in that of the Edo period (Table 1). Squatting posture may not be a main cause of this character.Squatting number indicates to some extent the degree of habitual postures such as squatting and other sitting postures which are characterized by strong flexion of knee joint. The mean values of the squatting number in the Jomon, Edo and recent periods are 3. 10, 3.05 and 3. 05, respectively. All these three numbers are smaller than the range 3.30 proposed by SIDDIQI (1934) and show the presence of habitual squatting and such other sitting postures in Japanese (Tables 2 and 3). In the Edo and recent periods the factor of the upright sitting may also be significant.CHARLES' facet is the antero-superior extension of posterior margin of medial articular surface of femur due to the compression against the semilunar cartilage in knee flexion. The size of CHARLES' facet in the Jomon period is larger than that in the Edo and recent periods (Table 4). This characteristics may be considered to show the influence of squatting posture and upright sitting.Squatting facet of talus should be considered to be a whole complex of foward extention of trochlea surface which may consist malleolar extention, medial extention, lateral extension lateral facet, abnormal surface of groove of neck and other facets. In Jomon period, all types of squatting facet are observed and are well developed as compared with those of recent period (Table 5). It seems that the habitual squatting is very common in Jomon period.Inferior facet of tibia corresponds to the squatting facet of talus. The frequency of occurrence of lateral inferior facet in Jomon period is higher than that in the Edo and recent periods (Table 7). The inferior fossa is formed by compression of talus neck when ankle joint is strongly flexed dorsally in squatting posture. The ratio of sagittal length of inferior fossa to sagittal length of inferior articular surface in Jomon period is larger by 2σ than those in the Edo and recent period (Table 6).The cause of these characteristics is so complicated that the interrelation among these characteristics are not clear except for the correlation between Squatting facet of talus and Inferior fossa of tibia, both of which are caused by habitual dorsiflexion of ankle joint. (Fig. 3-28). The interpopulation difference of these characteristics probably indicate the difference of environment such as mode of life rather than the genetical difference.Judging from the findings mentioned above, habitual squatting in Jomon period may be so common as in Punjabis (CHARLES, 1894), Australian aborigines (WOOD, 1920) and Indians (SINGH, 1959). It is suggested that in Edo period especially in urban district the proportion of habitual squatting was decreased and that of upright sitting was increased, being accompanied with the deffusion of mat-using. As for crosslegged sitting there is no available characteritics. The degree of sexual differences of these characteristics are generally in order of the Edo, recent and the Jomon period. The largest sexual difference in the Edo period possibly be due to the difference of mode of life under the feudal society. There can not be seen any difference between right and left sides in every characteristics.