120 



THE SKELETON 



V. Appendicular Elements (Bones of the Visceral Arches) 



(A) Cartilaginous 

 Malleus, Incus, and 



Stapes The ossicula auditus. 



Mento-Meckelian portion 



of the lower jaw SmaU part on either side near to the symphysis menti. 



Tympano-hyals and Stylo- 



hyals Styloid processes of the temporal bones. 



Epihyals Stylo-hyoid ligaments. 



Cerato-hyals Lesser cornua of hyoid bone. 



Thyreo-hyals Greater cornua of hyoid bone. 



Basi-hyals Body of hyoid bone. 



(B) Membranous 



Mandible The lower jaw excluding a small portion near symphysis. 



Tympanies The tympanic plates. 



Pterygoids The medial pterygoid plates. 



Palatals The palate bones. 



The Skull at Birth 



The skuU at birth presents, when compared with the adult skull, several important and 

 interesting features. Its peculiarities may be considered under three headings: — The peculiar- 

 ities of the fcetal skull as a whole; the construction of the individual bones; the remnants of 

 the chondral skull. 



(1) The General Characters of the Foetal Skull 



{The most striking features of the skull at birth are, its relatively large size in comparison 

 with the body, and the predominance of the cranial over the facial portion of the skull (8_to 1); 

 the latter is, in fact, very small. 



Fig. 143. — The Cranium at Birth. (Viewed from above.) 





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The frontal and parietal eminences are large and conspicuous; tlio sutures are absent; the 

 adjacent margins of the bones of the vault are separated by septa of fibrous tissue continuous 

 with the dura inator internally and the pericranium externally; hence it is difficult to separate 

 the roof bones from the underlying dura mater, each being lodged, as it were, in a dense mem- 

 branous sac. The bones of the vault consist of a single layer without any diploe, and their 

 cranial surfaces j)resent no digital impressions. Six membranous spaces exist, named fonta- 

 ncUos: two are meiiian, the frontal [fonticulus frontalis; niajorl being anterior and the occipital 

 [fonticulus occipitalis; minor] posterior. Two exist on each side, termed anterior [fonticulus 

 sphonoidalis) and posterior [fonticMilus mastoideus] lateral fontanelles. Each angle of the pari- 

 etal bones is in relation with a fontanelle. The anterior fontanelle is lozenge-shaped, the poste- 

 rior triangular. The lateral fontanelles are irregular in outline. The lateral fontanelles close 

 soon after birth; the occipital fontanelle clo.ses in the first year, and the frontal during the second 

 year. 



