THE DESCRIPTION OF A NEANDERTHALOID AUSTRA-

More documents

Recommendations

Info

38 A. St N. Burkitt and J. I. Hunter only by narrow nasal bones. In many Australian skulls they are supported by a relatively large medial angular process. The molar teeth are supported by the vertical ridge of the maxilla, which transmits the strains received by it to the zygomatic bone. Thereafter the strain is mainly supported by the fronto-sphenoidal process of this bone. From thence it passes to the external angular process of the frontal. The result of this increase of strait, leads, we believe, to increased bone deposition in the vertical ridge of the maxilla in the zvgomatic bone, and in the external angular process of the frontal bone. The fronto-sphenoidal process of the zygomatic bone and the external angular process of the frontal bone, are often markedly tuberculated on this account. This increase of bone formation as already shown also extends to and rounds off the orbital margin. When a low sloping forehead and a depressed nation are combined with massive jaws and teeth, as is often the ease in the Auistralian aboriginal, the siipraorbital ridges tend to be enormously developed (cf. Thomson (18)). Elevation of the frontal bone accompanied by a decrease of masticatory power, causes a diminution in size of this torus. The diminution first occurs over al) area between the strong medial angular process and arcus superciliaris medially and the tuberculated lateral angular process laterally, to each of which, the stresses from the maxilla are directly transmitted; this intermediate area becomes the planmm supraorbitale. In this region the elevated frontal bone is sufficient support without the addition of a toruis. The zygomatic arch also serves, through its inferior border, as a rod of resistance against the mandibular force as well as a support for the masseter. These factors again demand that this arch should be stout and strong. (b) Prognathisim. The general prognathism of the facial region of No. 792 was measured by Fraipont's method on the diagram of the norma lateralis (fig. 1). The line drawn from the glabella at rioht angles to the glabella-lambda line, passes in this ease through the alveolus of the second incisor. Klaatsch found in the specimens of the Roth collection that it passed through the first premolar or more posteriorly; this is in agreement with Fraipont's results. No. 792 shows that the prominence of the glabella so greatly influences the position of this line that, in calvaria in which it is markedly developed, reconstruction of the facial region cannot be carried out on the assumption that the above-mentioned line will pass through the premolar region without allowing for a great margin of error (12-13 mm. in No. 792). A second line parallel to the vertical line through the glabella and touching the most prominent point of the incisors (approximately determined owing to the teeth being absent), cuts the glabella-lambda line 4 mm. in front of the glabella (see fig. 2). This is considerably below the lowest figure quoted by Klaatsch, viz., 8 mmnm. in the Kalkadunii skull (R. 62). Again, the prognathic angle between lines from prosthion to glabella and prosthion to inion, is 820. The greater the facial projection the lower is this angle. Klaatsch records it as low as 70° and as hioh as 810 in the Roth series. Therefore, when measured
Description of a Neanderthaloid Australian Skull 39 by these methods, No. 792 appears to be more orthognathic than any in the Roth series. Flower's gnathic index which is independent of the degree of development of the glabella, places it well within the limit of orthognathic skulls, the index being 95X23. Turner(19) records five orthognathous male specimens and Duckworth (7) found the range in the Cambridge Collection to be 93X4 to 108-7 in males and 95 to 108-7 in females. Though apparently No. 792 is orthognathic, there is a decided tendency to alveolar prognathism. A measure of this was obtained by recording the angle between the following lines: (1) The line of the alveolar margin in the norma lateralis, and (2) The line from the naso-spinale to the prosthion. The angle proved to be 680. The greater the projection of the alveolar process the smaller will this angle become. For purposes of comparison, we have measured this angle in Klaatsch's selected specimens from the Roth series and the following results were obtained shown side by side with the figures obtained by Fraipont's method and by measuring the glabella-prosthion-inion angle: R. 2 ... ... ... ... R. 12 ... ... ... ... R. 16 ... ... ... ... R. 24 ... ... ... ... R. 28 ... ... ... ... R. 57 ... ... ... ... R. 60 ... ... ... ... R. 62 ... ... ... ... R. 80 ... ... ... ... Stuttgart 1719 ... ... ... B. 10283 (W.A., Sydney Museum) London Collection, S. 1406 ... No. 792 ... ... ... ... European (Australian Museum) Distance on Angle of alveolar glabella-lambda line Glabella-prosthion prognathism of (Fraipont) inion-angle maxilla 25 mm. 700 640 11 80 62 22 70 62 20 72 55 19 72 67 24 70 56 19 74 50 8 81 68 12 71 60 24 69 64 23 2348 This table at once shows that No. 792, though orthognathic, has definite alveolar prognathism. It also shows the three types of prognathism which are possible. There may be combined (1) an alveolar projection with a general facial prognathism (R. 2, R. 24, R. 57, R. 60, B. 10283, N. 1406, R. Coll. of Surgeons), (2) an alveolar projection without a general prognathism as in No. 792, R. 80, R. 12, (3) absence of facial prognathism and also of any marked degree of alveolar projection (R. 62, European). R. 80 and R. 12 also show that the ape-like horizontal condition of the sub-nasal region found in aboriginals is not necessarily associated with general facial prognathism, so that orthognathic skulls may thus preserve this primitive sub-nasal projection (cf. Topinard (19, 23)). A sagittal section of the skull illustrates further the modern characteristics observed in the facial region of No. 792. The pituitary angle measured 121° 70 73 82 76 44 45 65 73
Page 1 and 2: THE DESCRIPTION OF A NEANDERTHALOID
Page 3 and 4: Description of a NVeeanderthaloid A
Page 5 and 6: Description of a Neanderthaloid Aus
Page 7: Description of a Neanderthaloid Aus
Page 19 and 20: Description of a Veanderthaloid Aus
Page 25: Journal of Anatomy, Vol. LVII, Part

THE DESCRIPTION OF A NEANDERTHALOID AUSTRA-

Create successful ePaper yourself

Delete template?

Save as template?