376 Measurement of Internal Capacity of Skull 
(ii) the two inions can both be fixed, but the inferior may be so far more marked 
than the superior that without question it would be treated as the inion on the 
living head, (iii) no inion at all can be determined with any certainty. Testing 
the living head one may say that if an inion can be fixed, one is not definitely 
certain whether it is the superior or inferior unless both can be determined. That 
more often than on the skull itself a cautious observer would decline to make any 
dogmatic statement as to the position of the inion at all. In fact on the skull 
there is often grave doubt, on the living head there is usually doubt and often 
gravest doubt as to where the inion should be located ; and an occipital torus or a 
bathrocephalic network of ossicles, both not uncommon in English skulls, may 
completely put out any seeker for the inion on the living head. In short while it 
is highly undesirable to use the inion instead of the opisthion in any cranial 
investigation, the introduction of the inion into measurements on the living head 
is even more to be deprecated. 
To illustrate these points we have investigated the inion on an important series 
(L.S.) of 116 English skulls. There were 50 (/ and 66 $. Among these, owing 
to defects of one kind or another, 7 cT and 6 % had no inion-opisthion distance 
measurable. The remaining crania we placed before Professor G. Thane and asked 
him to determine the position of the superior and inferior inions. He most kindly 
consented to give us all the advantages of his anatomical experience, and we have 
the following results : 
Of the remaining 43 ^ and CO $ skulls the inion was " unrecognisable " or 
" undefinable " in 10 $ skulls, it was " very doubtful " in 1 and 2 $ skulls, and 
" vague " in 2 ^ and 10 % skulls ; thus the ^ skull gives usually a more marked 
inion than the $ skull. The superior inion was determinable more or less 
accurately in 41 </ and 43 % , the inferior in 28 and 23 $ . In 6 $ and 2 </ 
cases the inferior inion only was distinguishable ; only in 5 </ and 3 $ the two inions 
sensibly coincided. On the living head we very much doubt whether any precise 
inion could have been determined at all in about ^ of the $ and ^ to ^ of the 
cases. A prominent point would have been taken, but whether it would be the 
inion at all, and if so whether it was the inferior or superior would not be 
determinable. The difference between the position of the two inions amounted at 
a maximum to 11 mm. in the and 18 mm. in the $ ; the average differences 
between them being 5 mm. in the and 8 mm. in the 
The following are the results of measuring the inion-opisthion distance in mms. : 
Inion 
Male 
Female 
Meun 
Standard Deviation 
Mean 
Standard Deviation 
Superior Inion ... 
Inferior Inion ... 
47-0 
42-3 
4-7 
47-2 
39-2 
5-6 
