GROWTH OF THE SKULL. 233 



second period begins. This is marked by growth in all directions, the gradual rounding off of 

 the eminences of the vault, the progress of the mastoid, the strengthening of ridges, the greater 

 curving of the zygomatic arches, and the increase of the face. This last is due chiefly to the 

 advance of the nose, the gain of the superciliary eminences, and the increase of the lower jaw. 

 The rise of the basilar process increases and the occipital condyles stand out more from the bases 

 at the front edges. These processes are nearly finished in the female by nineteen and in the 

 male one or two years later, though, especially in the latter, they require several years more for 

 their absolute completion. The thickness of the vault is very nearly reached by puberty. At 

 seven the frontal sinus is only as large as a pea. Its development is not completed before the 

 twentieth year. There is no means of knowing whether or not it then entirely ceases. 



The orbit bears nearly the same proportion to the cranium at all ages ; laut at birth it equals 

 about one-half of the height of the face, and in the adult rather less than one-third. At birth the 

 axis of the orbit is horizontal. While sometimes the transverse diameter of the base of the orbit 

 is much the larger, this does not seem to be always so. As the face grows the \'ertical diameter 

 increases rapidly, so that, according to Merkel, at five the base lacks only two or three millimetres 

 of the adult height, which it gains in the next two years. The full breadth is probably not 

 attained before puberty. 



The changes in the nasal cavity are important as an essential element in the growth of the 

 face. At birth the line of the hard palate, if prolonged back, would strike near the junction of 

 the basilar process and sphenoid ; at three it strikes near the middle of the basilar ; at six, the 

 front edge of the foramen magnum, which is nearly or quite the condition of the adult. The 

 measurements of the vertical diameter of the choanae are important from their significance with 

 regard to both the nose and the pharynx. At birth the height is from five to six millimetres 

 (se\en millimetres is exceptional) and the breadth of each opening very little greater. At from 

 six months to a year both diameters have doubled, their proportions remaining unchanged. 

 There is little change before the end of the second year, when the height increases more rapidly. 

 Thus they change from circular to oblong openings. It is not till after puberty that the height 

 exceeds the distance between the internal pterygoid plates. 



HEIGHT OF POSTERIOR NARES. 



Authority. Age. 



Disse 4 



Disse 5 



Escat 5 



Escat 8 



Dwight 7 or 8 



Dwight 7 or 8 



Dwight 10 



Dwight II 



Dwight 14 



Escat 14 



Dwight  15 



Dwight i6>^ 



Dwight 17 



Dwight 18 



Dwight . . 19 



Escat i5toi8 ( 



The Closure of the Sutures. — The occipital bone unites with the basisphenoid at the 

 cerebral aspect about seventeen and on the outside of the skull some three years later. The 

 lower end of the suture between the occipital and the mastoid process is one of the first to close. 

 We have seen it lost in a skull of fourteen, of which the other bones were almost falling apart. 

 No doubt this was exceptionally early. The closure of the great sutures of the vault ^ ( to which 

 the term is usually applied) begins on the inside of the skull, probably before thirty, at the lower 

 ends of the coronal and at the back of the sagittal, and spreads irregularly. The process is 

 generally far advanced before it appears on the outside. The closure of the sutures on one side 

 of the head does not necessarily follow the same course on the other. It has usually begun on 

 the outside by forty, although the sutures are still distinct. They probably are nearly or quite 

 obliterated on the inside by fifty-five. The apex of the lambdoidal suture is one of the last 

 points to persist internally. It is impossible to state with accuracy the time at which the 

 sutures disappear on th0 outside, as this may never occur, and the process throughout is utterly 

 irregular. All may be gone very early or all may be distinct at an advanced age. \\'hen the 

 metopic suture fails to close in early childhood it is one of the very last to disappear. It is 

 unsafe from the sutures alone to draw any conclusions as to the age of a skull. 

 The weight of the skull in both sexes is greatest from twenty to forty-five.^ 

 The changes in old age are essentially atrophic. The most striking is the absorption of 

 the alveolar processes ; this, however, may occur prematurely from the loss of teeth. The 

 angle of the lower jaw becomes much more obtuse. The thin parts of the face and of the base 



^ Dwight : The Closure of the Cranial- Sutures as a Sign of Age, Boston Medical and Sur- 

 gical Journal, 1890. Parsons : Anthrop. Institute G. Brit, and Ireland, vol. xxx, 1905. 

 ^Gurriere and IMassetti : Rivista speriment. di Freniatria e de Med. legale, 1895. 



