LECTURE II. 39 



ginous or membranous base from separate osseous points, some 

 of which are symmetrically placed on both sides of the median 

 line, others lie in the central line. Increasing in growth — the 

 laws of which Welcker has recently established, — the bones ap- 

 proach each other and are finally connected by sutures. 



Thus it is well known that in new-born children the sutures 

 are not closed on the top of the head : the openings are the so- 

 called fontanelles. The anterior or the large fontanelle is of an 

 oblong shape, and corresponds to the junction of the sagittal 

 and coronal sutures, the posterior, triangular in shape, is situated 

 at the junction of the sagittal and lambdoid sutures. These 

 fontanelles usually close in the course of the first year. The 

 frontal suture closes sooner. Synostosis of the sphenoid and 

 occipital bone frequently takes place at maturity, so that some 

 anatomists* have described them as one bone. All these sutures 

 are often closed in old age. Premature closing is frequently 

 the cause of the arrest of cerebral development. The order in 

 which the sutures close appears to be connected with the 

 development of individuals and races, as we shall see in the 

 sequel. 



Some of the osseous points from which the cranial bones are 

 developed may be observed as prominences in the adult skull. 

 This is not, however, always the case ; in some crania they are 

 obliterated, in others very perceptible. Such are the frontal 

 eminences (tubera frontalia) above the eyebrows, the parietal 

 protuberances (tubera parietalia), and the occipital prominence 

 (tuber occipitale) in the centre of the squama occipitis. These 

 prominences are very distinct in the infant, and if, as is done in 

 the annexed figures, the outhnes of the embryonal bones are 

 marked on the adult skull, and the corresponding prominences 

 superposed, we obtain a good idea of the growth of the respec- 

 tive bones from birth to adult age. 



The base of the head formed by the three cranial vertebrae is 

 of great importance, as it determines the development of the 

 cranium, as well as that of the face ; the cranium, as regards 

 development and interpretation, being only a radiation of the 

 parietal parts of the base, and the face being appended to them, 



* Meckel especially. — Editor. 



