Extraocular muscles and their relationship to the accessory abducens nucleus in rats as studied by the horseradish peroxidase method.

1) Studies were made of the accessory abducens nucleus and its relationship to the extraocular muscles besides the retractor bulbi muscles in the rat. 2) All the extraocular muscles had nerve fiber connections from the accessory abducens nucleus besides the retractor bulbi muscles. 3) The relationship between the accessory facial nucleus and accessory abducens nucleus was investigated. The accessory facial nucleus was located from dorsal of the principal facial nucleus to the medial proximal part of the descending part of the facial root fibers, while the accessory abducens nucleus was located from the medial distal part to the descending part of the facial root fibers.