A clinical study of the skull / by Harrison Allen.

  • Harrison Allen
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: A clinical study of the skull / by Harrison Allen. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    NOTES ON SOME OP THE FORAMINA OF THE SKULL. The foramina of the skull are chiefly of interest in exhibiting re- tentions of embryonic states. The most striking of these states are seen at the base of the skull, at the region of the union of the vomer with the sphenoid bone and the sphenoidal processes of the palatal bone and pterygoid process, as already seen1 (page 23). The foramina may be asymmetrical; the foramen ovale less so than the others. A second group of retention—variations is seen at the surface of the sphenoid bone, where it lies against the petrosal to form the petroso-sphenoidal suture. Along the lines of this suture are found the oval foramen, the spinous foramen, and the canalis innominata. The suture widens not infrequently at the outer end to form an opening, which may receive the name of the petroso- sphenoidal foramen. The oval, spinous, and petroso-sphenoidal foramina may be confluent, or the spinous and petroso-sphenoidal may alone unite, or the oval and the spinous. The canalis innomi- nata2 may be large or absent. In the skull up to the fourth year the spinous and ]Detroso-sphenoidal openings are always united. I have often remarked that the spinous foramen may be entirely absent on one side.3 In some lower animals, as is seen in the Vir- ginian opossum, the foramina retain throughout life the type seen in this disposition to coalescence. The development of the tympanic bone is peculiar, for instead of uniformly extending in all its proportions a large foramen is always seen on the bone at its inferior surface. The significance of the opening is unknown. The foramen is very variable in form and position. As a rule, it recedes with age from the aperture of the meatus, so that in adult examples the retained foramen is almost always a centimetre or more from the outer free margin. Examples of the retention of the 1 For a good example see No. 924, negro. 8 The foramina ovale are at times asymmetrical. 3 No. 142, Marquesas (A. N. S.), furnishes an example.