On pteric sutures and pteric bones in the human skull - DWC - KNAW

639
epÎptel'iCllm typicllm can show just the same condition as a sÎtllllwith
a nnilateral processus fl'ontalis of Lhe first type.
That in case of a uni1atel'a,l os epiptel'icllm typiCllID the l'ight
side is predominant to t!Je left one is dne to the predominance of
the fl'ontal pl'ocess of the first type on the 1eft side.
If at the side of the skull, opposite to an os epiptel'icum typicmn
a spheno-parietal sllture is fOllnd, then the same 1'ules hold for the
situation of this suture as by a unilateral frontal processj that part
of the Skllll that lies symmetl'ical to the ptel'Ïc bone can be inclllded
as weIl in the aJisphenoid as in the frontal Ol' pal'ietal bone.
n. I fOllnd an os epiptericum of the second type in 7 skulls; in
one on both sides anel symmetl'ical, in 5 on the l'ight and in one
on the left side. This pteric bone was always combined with a
fl'ontal process of the fb'st type. Fol' the composition of the ptel'ic
region of tbe opposite side of the Skllll in a llnilateral OCCl1l'l'ence
of such a pteric bone can be referred (0 the description of the
frontal process.
lIl. An os epiptel'icum of this type I fOllnd only ollee in a skull
as a little sutllral bOlle in a fronto-temporal slltl1l'e.
IV. Sevel'al oss a epipterica I observed in 4 sknlls; ahvays hvo
bone-pieces were present. In ::3 slmlIs they were on the l'ight j m one
on the left side.
Fol' tbe behaviollr of the side of the simIIs opposite to those
wiÓ1 two pteric bon es, I refel' to the descriptions befol'e mentioneel.
All in all I fOllnd ptel'ic bones in 42 &knlls, or 36.8 % that is
to say in 5 on both sides, in 23 on the l'ight and in 14 skuUs
on the left side.
This enumel'ation pl'oves that pteric bOlles are more of ten fOUlld
on the l'ight than on the left side, on the eontraiT the fusion of
the bone pieces in the pteric region with one of the surl'ounding
bones, specially the squamosal, happens more fl'equently on the left
than on the right side.
It is impossible to deeide by this stud)' the meaning of the
pteric bones.
The frequent occurrence of these separate bone.pieces in papuan~
simIIs is not favourable for RANKJi]'S theory, saying' they ought to
be eonsidered pathologica1.
Ontogenetical and comparative anatolllical researches will be
necessary to explain this question of the anatomy of human skull.
41*
- 7 -