Chapter XXXV: Munsee Crania: Middle Lacerated Foramina; Posterior Lacerated

FORAMINA

--------------------+----------+----------
| 7 males |12 females
+-----+----+-----+----
|Cases|Per |Cases|Per
| |cent| |cent
--------------------+-----+----+-----+----
Medium (about as | | | |
average in whites) | 1 | 14 | 1 | 8
Submedium | 5 | 71 | 3 | 25
Small | 1 | 14 | 8 | 67
---------------------+----------+----------
| 7 males |12 females
+-----+----+-----+----
|Cases|Per |Cases|Per
| |cent| |cent
---------------------+-----+----+-----+----
Of equal size | 1 | 14 | 1 | 8
Right larger | 5 | 71 | 8 | 67
Left larger | 1 | 14 | 3 | 25
---------------------+-----+----+-----+----

The posterior lacerated or jugular foramina are of interest chiefly because of their frequent and often marked inequality in size, which signifies inequality in the size of the lateral sinuses and especially of the internal jugular veins. The right foramen is frequently larger than the left, a phenomenon which has been associated with the prevailing right-handedness in man. In the nineteen Munsee skulls in which the foramina could be examined, they are of about equal size in only two instances; the right is larger in thirteen, or in two-thirds of the cases, while the left is the larger in only four instances. As the proportion of left-handed persons among the Indians averages only about three per cent, it is evident that in some instances the relation between a larger jugular canal and habitual greater use of the arm of the same side would not maintain; besides, we know the motor centers for the right arm and hand to be on the left side of the brain. Possibly greater blood pressure on the right side in right-handed persons, due directly and mechanically to the greater muscular activity on that side, would be a more satisfactory explanation.

_Depressions of the petrous portions._—In examining the petrous parts in the usual way, with the skull turned base upward, it is observed that in modern men of all races, in the majority of cases, these parts are more or less depressed below the niveau of the surrounding parts. In reality, of course, the surrounding parts have been pressed outward by the developing brain, while the prismatic and resistant petrous parts remained behind. The grade of depression of the petrous parts stands generally in close correlation with the size of the middle lacerated foramina and is of parallel significance.[45] Among the anthropoid apes even a slight depression of the petrous portions is very rare, and most frequently, especially in the orang, these portions rise slightly above the surrounding structures. In the African negro, and occasionally in individual skulls of other inferior races, they are level with the surrounding parts. In better developed negro skulls, as in the majority of those of other primitive peoples, they are slightly to moderately depressed. In white men, and in superior skulls in general, the depression is frequently pronounced, especially, it seems, in the brachycephals. The Indian stands in a practically intermediate position between superior whites and the negroes, and the Munsee are no exception. In two of the skulls the depression is well marked; in three males and seven females it is less than the average in whites; and in two males and five females it is only slight. The females, it will be noted, make a poorer showing in this respect than the males.

[45] See Hrdlička, Certain Racial Characteristics of the Base of the Skull, Science, 1901, p. 309; Proc. Assoc. Amer. Anatomists, 15th Sess., in _Amer. Jour. of Anatomy_, I, 1901-2, pp. 508-9.