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120

Cunningham Memoirs.

all the change that occurs. The coronal line is by no means fixed. In
its early condition the field of the parietal bone in the anteroposterior
direction is relatively less than in the adult, and by its subsequent growth
forwards it comes to cover a relatively greater part of the island of Reil.
This is particularly noticeable in connexion with the lower fifth of the
coronal suture. Here the anterior border of the parietal bone in the process
of cranial growth sends forward a squamous portion which gradually
overlaps the corresponding portion of the posterior border of the frontal
bone. This is rendered evident in the four skulls which are figured in

Fig. 29.—Lateral view of the skull of a child about fifteen months old. The internal sutural lines are
shown by a series of perforations made from the interior. They can be compared with the
external sutural lines.

pages 119-122. In these the cranial wall has been drilled along the lines
of the sutures as these are seen on the interior of the cranium. By this means
the posterior border of the frontal bone is delineated on the outside of the
different skulls, and it will be noticed that as the period of childhood gives
place to that of full growth the overlapping process of the parietal bone
increases in extent and carries forward the lower part of the external
coronal line ; and it can be easily proved by measurements of the cranium