A stereotaxic apparatus for the study of the central nervous structures in the pig.

An apparatus has been developed derived from the Horsley-Clarke principle. Specific requirement was to use large breeds of pigs from weaning to adult age (5 to 120 kg). The pig auditory canals are oblique; the measurement of the corresponding angles was achieved by means of two interconnected barrels, used afterwards to fix the ear-bars. The wide variability of the skull morphology led to the systematic use of ventriculography with a liquid of contrast. Consequently the pieces allowing the head fixation in the stereotaxic apparatus were designed to avoid any shadow on the brain area. As it was not always possible to localize the commissura anterior, the anterior border of the recessus preopticus was chosen to determine, together with the commissura posterior, the reference horizontal plane. The antero-posterior coordinates were counted from the anterior border of the commissura posterior. The methodology, which has been tested in a wide range of pigs, is discussed in relation with the methods used for other animal species.