582 



ANATOMY OF VERTEBRATES. 



the neural spine (superoccipital, 3), and next with the centrum 

 (basioccipital). This afterwards coalesces with the centrum (basi- 

 sphenoid, 5, c) of the parietal segment. With this centrum also the 



403 



1' ' ia 



Vertebral segments shown In the Human foetal skeleton. CXL. 



neurapophyses, called ' alisphenoids,' n, the centrum of the frontal 

 vertebra, called ^ presphenoid/ and its neurapophyses (orbito- 

 sphenoids, 10), become anchylosed. The neural spine (parietal, 7) 

 retains its primitive distinctness, but is enormously expanded, and 

 is bifid, in relation to the vast size of the brain in Man. The 

 parapophysis (mastoid, fig. 404, c) becomes confluent mth the 

 otic capsule (petrosal), the tympanic, d, squamosal, «, and with 

 the pleurapophysis, called ' stylo-hyal,' fig. 403, 38, of the haemal 

 (hyoidian) arch. The h^emapophysis is ligamentous, save at its 

 junction with the haemal spine when it forms the ossicle called 

 ^ lesser cornu of the hyoid bone,' ib. 40, the spine itself being the 

 basi-hyal, 41. The whole of this inverted arch is much reduced 

 in size, its functions being limited to those of the tongue and 

 larynx, in regard to taste, speech, and deglutition. The neur- 

 apophyses (orbitosphenoids, 10) becoming confluent with the cen- 

 trum (presphenoid, 9) of the frontal vertebra, and the latter 

 coalescing with that of the parietal vertebra, the compound bone 

 called ' sphenoid ' in Anthropotomy results, which combines the 

 centrums and neurapophyses of two cranial vertebra?, together 

 with a diverging appendage (pterygoid) of the maxillary arch. 



The knowledge of the essential nature or ' general homology * 

 of such a compound bone gives a clue to the phenomena of its 

 developement from so many separate points, which neither em- 



