Topographical anatomy and measurements of selected parameters of the rat temporal bone.

On the basis of dissection of 24 bones of 12 black rats a systematic anatomical description was made and measurements of selected size parameters of the temporal bone were taken. Besides the main air space in the middle ear, the tympanic bulla, there are also additional air cells, namely the anterior and posterior epitympanic recesses, containing the head of the malleus and the body of the incus. On the side of the epitympanic recesses the following are easily accessible: the malleus head and the core of the incus, the superior and lateral semicircular canals and the facial nerve. On the side of the ventral tympanic bulla it is easy access to both windows and the cochlea. 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 11 mm. It is worth mentioning that both the vertical and horizontal dimensions of the scala vestibuli and scala tympani do not even exceed 0.7 mm in the basal turn, and are significantly decreased to tenths of a millimetre in further turns. This needs to be taken into consideration during all experiments requiring the introduction of examining instruments into the cochlear scala.