_a n o f_ are equal to the mouth.

_a c_ and _a f_ are equal to the space between one eye and the
other.

_n m o f q r_ are equal to half the width of the eye lids, that is
from the inner [lachrymatory] corner of the eye to its outer corner;
and in like manner the division between the chin and the mouth; and
in the same way the narrowest part of the nose between the eyes. And
these spaces, each in itself, is the 19th part of the head, _n o_ is
equal to the length of the eye or of the space between the eyes.

_m c_ is 1/3 of _n m_ measuring from the outer corner of the eyelids
to the letter _c_. _b s_ will be equal to the width of the nostril.

[Footnote: See Pl. XII.]