Variability of origin of serratus anterior muscle in Japanese.

The observations on 567 male and 251 female Japanese cadavers revealed that there was a wide variation of the lowermost origin of the serratus anterior muscle ranging from the 6th to the 12th rib. The most frequent cases in males were of the 8th rib type (42.5%), whereas those in females were of the 9th rib type (43.3%). There was a statistically significant difference in the distribution of the muscle origin between the sexes. The observations also showed that bilateral symmetry of the muscle origin was preponderant over asymmetry, the symmetric cases forming about seven-tenths of all individuals without sex distinction.