In the third frontal convolution are situated Broca's centres, which are believed to be the seat of articulate speech; while along Rolando's fissure, in the ascendant convolutions, is the locality designated by physiologists as the motor centres.

The occipital lobe is the location of the zone of sight; and the temporal lobe, that of hearing.

It is important for us to observe the volume of the brain, and therefore that of the head, in relation to the rest of the body; it is enormous in the embryo; and even at birth and during childhood the head is quite voluminous as compared with the body, as appears from the diagram in Fig. 16, in which a new-born child and an adult man are reduced to the same scale, each retaining his relative bodily proportions. In Fig. 22 a new-born child is shown in two positions: from the front and from behind; the head is very large and the cranial nodules are plainly visible. Figs. 80 and 81 represent the same child at the age of six months and a year and a half; in the first picture the head is still very large as compared with the body, and the forehead protrudes (infantile forehead); in the second, the proportion between head and body has already altered.

A knowledge of the laws governing the growth of the brain is of particular importance in relation to pedagogic anthropology.

Fig. 77.—Cerebral hemisphere, internal face.

Within the last few years anthropologists have established certain principles that are well worthy of notice:

  1. The child's head is normal when its volume and cephalic index come within the limits of normality (even if the shape appears abnormal: Simon, Binet, etc.).
  2. When the volume of the head is too small it frequently indicates psychic deficiency; when it is too large, even up to the age of twenty years, it indicates a predisposition to precocious mortality (see below).

Very frequently when the size of the head is larger than normal and is not due to pathological causes (rickets, hydrocephaly, etc.), it is associated with an excessive development of the brain, and also with an intellectual precocity. A high percentage of this type die before reaching the age of twenty years; and this fact confirms the popular belief that children who are too intelligent or too good cannot live long.

This indication alone ought to be sufficient to prove the pedagogic importance of the cerebral volume.