Measurements of selected parameters of the guinea pig temporal bone.

On the basis of dissections of 32 temporal bones of the guinea pig, measurements were taken of selected size parameters of the temporal bone. The measurements performed included external and internal size parameters of the bone. Among these were the following: the length, width and height of the external and internal auditory meatus, the length of the incudomallear complex, the height of the attic, the full length and height of the tympanic cavity and the parameters characterising the localisation of the external orifice of the facial nerve. The semicircular canals are relatively large, the lateral canal being the largest and the posterior the smallest. The length of the spiral canal of the cochlea does not exceed 16 mm. It is worth noting that both the vertical and horizontal dimensions of the scala vestibuli and scala tympani only exceed 1 mm in the basal turn, decreasing significantly in the further turns to as little as decimal parts of a millimetre. This should be taken into account during all tests which require the introduction of examining instruments into the cochlear scala.