["Hand clasping" and "arm folding". Population, hereditary, and neurophysiologic aspects].

The data have been obtained showing that the hand clasping does not constitute a hereditary trait. The frequency of R- and L-types makes nearly 50% in all age groups. Possible relation of this trait with left handedness on non-genetic basis is discussed. The frequency of R- and L-types of arm folding is age dependent. The association of this trait with brain motor asymmetry and asymmetry of finger dermatoglyphics has been established. The correlation calculated by means of the threshold model for multifactorial traits is significant in the pairs of monozygotic twins for T-type, and insignificant for L-type. This may reflect a non-uniform degree of hereditary effects on the function of left and right cerebral hemispheres.