1955 年 63 巻 6 号 p. 225-233
We Know that the palmaris longus muscle is one of the most valiable muscles in the human body. It is frequently absent on one or both sides and there are
racial differences in the parcentage of absence of this muscle.
The stadies of this muscle in the living subjects are the most frequent, because of its easy accessibility to examination.
On the cadavers of Japanese several works have appeared, but so far as I have been able to ascertain, there appear to be no reference to work done by the
same method on living subjects.
As to method, it is sufficient to state that this relates only to the closed fist of the studied individual who was asked to flex his hand at the wrist with light opposition by the examiner. The tendon of the flexor carpi radialis thus appears clearly on the lateral side, while if it is present, that of the palmaris longus is in a medial position.
The author carried out examinations on about 500 (417 males and 116 females) adult subjects of living Japanese and hereditary research on 9 families.
The results of this study are tabulated as follows :
On one or both sides, the frequency of absence in persons is 5.5% in males and 9.5% in females. The percentage of absence in all arms examined is 3.6%. in vales and 6.0% in females. In the sexual difference the frequency of absence occurs pore often in females than in males.
The palmaris longus muscle is lacking more often from the right side than from the left.
In many races absence of the muscle more frequently occurs than has been noted among the Japanese among whom it is low and in this respect there are few discrepancies between results of this study and earlier reports on thee cadavers.
I believe that the absence of this muscle is a dominant hereditary trait.