ABSTRACT Brachial plexus morphology varies among species and is useful to understand forelimb phylogeny. Classifications of the Japanese raccoon dog and common raccoon dog ( Nyctereutes procyonoides ) are under discussion, and comparisons of brachial plexus morphology between them may provide clues to address this issue. However, brachial plexus morphology has not been investigated in Japanese raccoon dogs. Twenty brachial plexuses from 11 Japanese raccoon dogs were observed macroscopically, and the epineurium was then incised under surgical microscopy to trace the fascicles. The roots of brachial plexuses comprised ventral branches from the 6th–8th cervical nerves (C6–8) to the 1st thoracic nerve in 12 plexuses or to the 2nd thoracic nerve in eight plexuses. Macroscopically, nerves arising from the brachial plexus showed frequent variations. By fasciculus analysis, fasciculus components showed less variations than suggested macroscopically and most nerves showed the typical pattern (i.e., detected in more than 50% of halves), except for the caudal pectoral nerve. Moreover, patterns of communication among terminal branches, such as the axillary, radial, musculocutaneous, median and ulnar nerves, were analysed. Most frequently, we detected that the communicating branch between the axillary and radial nerves included fasciculi from C6 and C7 to the radial nerve, and that between the musculocutaneous and median nerves included a fasciculus from C8 to the musculocutaneous nerve. The details of brachial plexus morphology in Japanese raccoon dogs may provide an anatomical basis for comparing brachial plexus morphology between species.
Miyai et al. (Wed,) studied this question.