THE VEBTEBBAL CONSTITUTION OF THE SKELETON. 



121 



In the four classes of vertebrata, the head is constantly formed of four 

 vertebrae, which are determined as follows :" ' 



VERTEBKjE. 



CENTRUM. 



NEURAL ARCH, 



H/EMAL AKCH. 



Occipito-hyoide.il. j Basilar process ] Occipital (3 pieces). j Hyoideal appa- 

 i of the Oocipi- | Mastoid walls of the | vatus (5 pieces). 

 1 tal. , Tympanum. 



! Parieto-maxillary. 



Body of the pos- 

 terior Sphe- 

 noid. 



I Wing and pterygoid | Inferior Maxilla 

 I process of the pos | 5 pieces). 

 i terior Sphenoid. | 



I Squamous portion and 

 ; zyj;omatic process of | 

 ] the Temporal. 

 Parietal. 



Fronto-mandibular. | Body of the | Wing and pterygoid Jugal. 



Anterior Sphe- i process of the anterior Lachrymal, 

 noid. I Sphenoid. i Palatine. 



I Posterior Frontal and | Supeririiixillary. 



' its orbital process. : Premaxillary. 



' Frontal. 



Naso-turbinal. 





Vomer. 



Ethmoid. 

 Nasal. 



i Turbinated 

 I Subetlimoidal. 



The number of cephalic vertebrse is invariable, as each is destined to . 

 lodge the organs of one of the four senses. The occipito-hyoideal lodges the 

 principal organs of hearing; the parieto-maxillary osteodesm protects the 

 sense of taste ; finally, the organs of vision are sustained by the fronto-man- 

 dibular vertebra, while the naso-turbinal contains tlie sense of smell. 



It was therefore with reason that Geoffroy Saiut-Hilaire and Professor 

 Owen proclaimed that the type of construction of the vertebrated animals is 

 the vertebra 



SECOND SECTION. 

 The Akticdlations. 



CHAPTEE I. 



THE ARTICULATIONS IN GENERAL. 

 The different pieces constituting the solid framework of the animal body 

 are as has been said, united in such a manner that they can move one upon 

 the' other From this union results the articulations or articular joints, whose 

 construction will now be referred to in a general manner, before commencing 

 a particular description of each , ,, , 



To form articulations, the bones correspond to each other by certain 

 points of their periphery, which are named articular surfaces. Every articu- 

 1 Lavocat, ' Kouvelles (Studes sur le systeme vertebral,' 1860. 



