The "temporal bone" of human anatomy is composed of the transverse process, or parapophysis of the parietal vertebra (the mastoid bone or process), of an appendage of the haemal arch of the nasal vertebra (squamous bone), of the auditory sense capsule (petrous portion of temporal bone), of the pleurapophysis of the frontal vertebra (tympanic bone), and of the pleurapophysis of the parietal vertebra, or the styloid process. We will examine at present those elements only which are connected with the parietal segment.

The mastoid process (parapophysis) articulates by firm serrated suture with the posterior inferior angle of the parietal bone. It is nipple-shaped, rough externally for the attachment of muscles, excavated within into cells which communicate with the tympanum. Meckel, who incorrectly compares the petrosal bone to the body of a vertebra, passes by the mastoid process without further remark, than that it is of conical form, and situated behind the styloid process. It recieves the insertion of the trachelo-mastoid muscle, a slip of the longissimus dorsi, which extends longitudinally from the sacral diapophyses uninterruptedly to the parietal para-pophysis, the only oustanding lever possessed by that cranial segment. It is curious to remark, that the squamous portion of the temporal bone, an appendage of the nasal vertebra, and intercalated only to complete the lateral walls of the expanded cranium, simply overlaps the parietal bone; whilst the mastoid, or parietal parapophyses, articulates with the same bone by serrated suture.