This index is not exact and constant, like that for the cranium; in fact, in case a person loses his teeth the index is altered. At the present day, especially in the French school, the anterior or total facial index is taken into consideration, in which the vertical diameter is measured from the vertex of the head to the chin (Collignon), and, consequently, the index is always less than 100. The following is the nomenclature that results for the anterior facial index:
| Leptoprosopics | 62 and below |
| Mesoprosopics | from 62 to 66 |
| Chameprosopics | 66 and above |
If we take for the measure of length that of the visage, i.e., the distance between the middle point of the frontal line of roots of the hair and the chin, we obtain indices that are higher by 5 than those of the French school, namely:
| Leptoprosopics | 67 and below |
| Mesoprosopics | from 67 to 71 |
| Chameprosopics | 71 and above |
In many cases this index differs in the individual by as much as 10 from the cranial index, as I proved in my work on the population of Latium. Consequently, anyone who has a cranial index of 81 ought to have a visage index of 71, etc.
Contrary to what happens in the case of the cranium, the index of the face varies according to the age, the face being very short in childhood, and much longer in the adult.
Angles.—The angles distinguished by anthropologists are so numerous that it is impossible for us to take them all under consideration.
In the case of a living person, the angles may be measured directly with the aid of Broca's goniometer; the transverse branch passes across the subnasal point; the two antero-posterior branches are inserted, with the buttons with which they terminate, into the external auricular canals; the vertical branch, swinging on a hinge, is adjusted in such a way that the little rod which it carries at the end rests upon the ophryon.
This complicated instrument resembles an instrument of torture and could not be applied to children; furthermore, it is difficult to adjust, and consequently the angles that it gives are inexact: every muscular contraction causes the angle to vary. For this reason the goniometer is impracticable.
If, by means of an instrument we trace the projection of the facial profile, the facial angle may be taken on such a drawing; it may also be traced and calculated on a photograph taken in profile.