The orientation of the semicircular canals in the guinea pig.

In 10 adult guinea pigs the stereotaxic coordinates of a series of points along each osseous semicircular canal were analysed to yield an equation of that canal plane in stereotaxic space. Angular relationships among the canal planes and between the canal planes and the major stereotaxic planes are presented together with the optimal positions of the head for physiological stimulation of each canal or pair of synergistic canals. The planes of the semicircular canals in each labyrinth are not perpendicular to one another and the planes of contralateral synergistic canals depart from parallelism by about 30 degrees.