232 



HUMAN ANATOMY. 



The/ace, while helping to form the orbit and nasal cavities, is essentially for the jaws, and 

 the jaws for the teeth. The greatest change in the head after birth is the downward growth of 

 the face. According to Froriep, in the infant the face is to the cranium as i to S ; at two years 

 as I to 6 ; at live, as i to 4 ; at ten, as i to 3 ; in the grown woman as i to 2.5 ; in the man 

 as I to 2. On contrasting the front view in the infant and adult, counting as "face" all below 

 a line at the top of the orbits and as "cranium" all above it, it will be seen that in the infant 

 the cranium forms about one-half and in the adult much less. The lower border of the nasal 

 opening is at birth but very little below the orbit. A line connecting the lowest points of the 

 malar bones passes at this age midway between the nasal opening and the border of the alveolar 

 process. At birth the nasal aperture is relatively broad ; its Icfwer border is not sharply marked 

 of? from the face A line from the nasal spine' runs outward to end inside the cavity, and the 

 crest from the outer border is still rudimentary, ending shortly on the front of the face, so that 

 at the outer angle there is no distinct separation between face and nasal cavity.^ The nasal 

 cavity is shallow, the posterior nares very small. The vomer slants strongly forward. Tne 

 lower jaw is small and the angle of the ramus very obtuse. The alveolar processes are rudi- 

 mentary. The breadth of the skull at its widest equals or exceeds the combined height of the 



Fig. 262. 



Posterior fontanelle 



Interparietal suture 



Anterior fontanel! e^ 



The skull at birth, from above. 



cranium and face in the infant ; in the adult it is but three-quarters of it. The breadth of the 

 face is to its height as 10 to 4 at birth, and about as 9 to 8 in the adult. 



Merkel divides the growth of the head into two periods, with an inter\ening one of rest. 

 The first ends with the seventh year, and is followed by inactivity till puberty, when the second 

 period begins. ^\\^ first period may be subdivided into three stages. In the first stage, reach- 

 ing to the end of the first year, the growth is general, but the face gains on the cranium. At si.x 

 nKDiiths the basilar process rises more sharply, which, with the downward growth of the face, has 

 an important effect on the shape of the naso-pharyn.x. The lower part of the nasal cavity gains 

 particularly. The posterior opening doubles its size in the first si.x months, to remain stationary 

 till' the end of the second year. In the second stage, to the end of the fifth year, the vault grows 

 more than the base, assuming a more rounded and finished appearance. Tlie face still gains 

 relatively, but grows more in breadth than in height. In the third stage, corresponding roughly 

 to the seventh year, the base grows more and the vault less. The face lengthens considerably, 

 Xh^t growth in the nasal chambers l^eing cliiefiy in the lower part. The head, though small, has 

 lost the infantile aspect. The foramen magninn and the petrous portion of the temporal have 

 reached their full size, and the orbit very nearly. The parietal and frontal eminences are still 

 very prominent. The mastoid is rudimentary. This condition lasts till puberty, when the 



' Macalister : Journal of Anatomy and Physiology, vol. x.xxii., 1898. 



