154 
DR. J. CLELAND ON THE VARIATIONS OE THE HUMAN SKULL. 
angle is subject to such, variations altogether independent of the position of the face, it is 
no wonder that, as Welcker has observed, “ the unprejudiced consideration of the whole 
skull in many instances exhibits a very different degree of prognathism from what the 
size of the nasal angle would indicate.” 
Lucae is in one sense right in keeping altogether out of view the position of the base 
of the skull in seeking to estimate the amount of what is generally understood by pro- 
gnathism and orthognathism ; for it is evident that the relation of the face-bones to the 
base was never examined by any of the writers who attracted attention to the degree of 
prominence of the face ; but, on the other hand, his method throws no light on the con- 
current causes of the general appearances which they have noticed, nor does it furnish 
an accurate index of the extent to which either of the appearances is present. For 
example, it might not be difficult to find two skulls tolerably similar in appearance as 
seen in vertical mesial section, and which might be considered to have as thus seen 
the same degree of prognathism, but one of which would have the auditory meatus 
placed on a much higher level than the other. In such a case the difference in posi- 
tion of the auditory meatus would be accompanied with a difference in the disposition 
of the zygomatic arch such as would materially affect both Camper's facial angle and 
the degree of prognathism as indexed by Lucae’s method. 
The foregoing remarks may serve to illustrate the uncertainty which invests the whole 
question of the varying relations of the face to the cranium, and may prepare us to in- 
vestigate those relations in detail. 
The orbito-nascd angle (column 24). — By this name may be designated the angle con- 
tained between two lines extending from the fronto-nasal suture, one to the optic fora- 
men and the other to the tip of the nasal spine of the maxilla. The tip of the nasal 
spine is chosen rather than its root, because it is a more definite point, and because the 
nasal spine is a characteristic portion of the maxilla independent of the teeth. The 
orbito-nasal angle in the foetal skulls is of sizes such as are found in adults ; but in the 
seventh and eighth month foetuses it is smaller than in those of the fourth and fifth 
months. In the infants at birth it has attained a greater size than it has either before or 
afterwards, but as childhood advances it becomes rather smaller than the adult average. 
Thus, if prognathism were to be taken as meaning projection of the face from under- 
neath the floor of the anterior cranial fossa, infants would have to be considered as 
exhibiting the maximum of prognathism, notwithstanding that in them the face is far 
smaller in proportion to the .cranium than it is in the adult. Observation on the living 
subject will fully verify in this respect the results of the measurements here given; 
for it will be readily seen that in infants and young children the sum of the orbito-frontal 
and orbito-nasal angles is much greater than in the adult. After birth the orbito-nasal 
angle diminishes apparently pari passu with the increase in the orbital length, dependent 
on the growth of the anterior lobes of the brain ; but the orbital length is further in- 
creased at puberty by the enlargement of the frontal sinuses ; and it is a remarkable and 
important fact that this is not accompanied with a further diminution of the orhito-nasal 
angle, but, there being about that time apparently a general growth of the face-bones, 
