M. L. TiLDESLEY 
255 
larger than the left), 28 where it was the left lateral sinus, and 13 in which it was 
impossible to decide between them. 
It seems reasonable to suppose that where the main stream of blood is directed 
down one side rather than the other, the outlet for the blood-vessel on that side 
will be larger than the one on the opposite side; and there was indeed a very 
noticeable inequality in the size of the two jugular foramina in a large proportion 
of skulls. Owing to the difference in shape of the two foramina, it was sometimes 
difficult to decide which was the greater when they approached each other in size. 
Our figures would, however, give a good approximation to the truth; they are: 
82 skulls in which the right jugular foramen was the greater, 32 the left, 13 equal. 
It will thus be seen that it is the right side which has much the greater number 
both of larger grooves and larger foramina. Can we rely upon the jugular foramina 
to tell us what is the arrangement of the sinuses? The answer is given by the co- 
efficient of mean squared contingency, as obtained from the following table, which 
is -6541 for uncorrected and -7036 with the class index correction applied. 
Greater Jugular Foramen 
Right 
Equal 
Left 
Totals 
Right 
79 
6 
4 
89 
Equal 
2 
5 
6 
13 
Left 
1 
2 
22 
2.5 
Totals 
82 
13 
32 
127 
This is for 127 skulls, and mean where no contingency exists will be of the same 
order as that for 130, which has been quoted already. The difference between this 
and the result obtained is roughly 8 times the probable error, and we may there- 
fore conclude that there is a very close relation between the two (though not a 
perfect one). This means that we can accept the evidence of the foramina as to the 
arrangement of the sinuses, if the more direct evidence of the grooves be un- 
obtainable. 
In connection with this subject my attention was directed to an interesting 
paper by Professor Elliot Smith* in which a relation is suggested between exterior 
occipital asymmetry and the direction of the main sinus. The argument briefly is 
as follows: The occipital poles of the cerebral hemispheres are frequently asym- 
metrical. Professor ElHot Smith estimates that in roughly 80 per cent, of 
Egyptian brains, the area of cortex containing Gennari's stria (the area striata) 
extends much further on to the outer aspect of the left hemisphere than on to the 
corresponding surface of the right hemisphere: often as far as 3 or even 4 cms. 
from the median line on the left, whereas on the right side the area striata barely 
crosses the edge of the hemisphere. "As a rule, this lateral part of the area striata 
* Anatomischer Anzeiger, Band xxx. pp. 574-578, Jena, 1907. 
