If we compare the head of an adult with that of an infant, and draw the well-known line of separation between the facial and the cerebral cranium, the difference in the reciprocal proportions between the two parts at once becomes apparent. The infant's face seems like a mere appendix to its cranium; and the mandible is especially small; in fact, very young children remain much of the time with their mouth open and the under lip drawn back behind the upper.
Fig. 109.—Face of inferior type. Prominence of angles of jaw (Gonia).
Fig. 110.
Fig. 111. Fig. 112.
a, eye; v, anterior brain; m, middle brain; s, frontal process; h, nasal septum; o, u, h, d, r, primitive embryonal formations, explained as being branchial (i.e., gill) arches; z, tongue; g, auditory fissure. Note the analogy between the different parts of the head in animals and in man; every species, however, has special embryonal characteristics.
Consequently, the growth of the face obeys laws and rhythms differing from those of the cranium, in comparison to which the face is destined to assume very different proportions by the time that the adult age is reached. The face grows much more than the cranium.