A statistical study on anatomical variation in the origin of the Japanese pectoralis minor muscle.

The origin of the pectoralis minor muscle of Japanese was studied in the dissection practice for medical students in our school of medicine and the incidence of the variation of the origin of this muscle was statistically studied and compared with that of American whites and American negroes. The most frequent types in Japanese were type 2-5 (the pectoralis minor muscle arising from the 2nd, 3rd, 4th and 5th ribs) in males and 2-4 in females on both thoracic sides. Type 2-4 in Japanese females was the most frequent among these three ethnological groups.