The Chondro-epitrochlearis, an Aberrant Slip of the Pectoralis Major

The chondro-epitrochlearis muscles were found in both sides of the upper extre-mities of a 59-year-old Japanese male. The anomaly consisted of two muscular fasciculi; the one arising from the most caudal part of the pars abdominalis of the pectoralis major and the other from aponeurotic sheet covering the dorsal surface of the pectoralis major. After crossing over the axilla the former fasciculus abruptly curved away from the parent muscle and joined with the latter. Both fasciculi ran down together along the antero-medial side of the arm as far as a point about 10 cm from the epicondyle, where they continued to the slender tendon to insert on the medial epicondyle of the humerus. Near the lower end of the arm the tendon was connected with medial intermuscular septum also. There existed the muscular arch of the axilla stretching between the latissimus dorsi and the coracoid process. The present chondro-epitrochlearis was innervated by the caudal pectoral nerve from the ansa pectoralis which also supplied the pars abdominalis of the pectoralis major and the muscular arch. The chondro-epitrochlearis would be an atavistic anomaly demonstrating the extent of the insertion of ancestral forms.