VEETEBEJS. 759 



maxillary, two nasal, two lacrymal, the vomer, two inferior turbinated 

 bones, two palate bones, two jugal bones, and, lastly, the two halves of 

 the lower jaw. 



(2172.) It is true that some slight exceptions occur : thus, forexample, 

 in the Cetacea the pterygoid bones remain detached ; in the Rodentia 

 the occipital is divided into a superior and inferior portion ; but in the 

 latter, the two frontal and the two parietal become consolidated into 

 one bone. 



(2173.) In Man the bones of the cranium become much less nume- 

 rous, inasmuch as all the elements of the occipital, of the temporal, of 

 the frontal, the intermaxillary, and the maxillary, composing the upper 

 jaw, and the two halves of the lower jaw, respectively coalesce ; and the 

 skull consists of but one-and-twenty bones, seven in the cranium, and 

 fourteen in the face. 



(2174.) Even this number is not the smallest ; for in some Monkeys 

 the nasal bones unite and become consolidated into one piece. 



(2175.) Having thus enumerated the different osseous pieces forming 

 the crania of all classes of vertebrate animals, we must next consider 

 them in another point of view, namely, as being continuations of the 

 spinal chain of bones, or real vertebrae modified in form and proportions 



1 conformity with the increased volume of the nervous masses they are 

 gained to enclose. "We must premise, however, that it is by no means 



2 itention to adopt unreservedly the theoretical opinions of those 

 mental writers who find vertebral elements in the bones of the face, 



i even in the nasal cartilages ; still, without overstraining the facts, 

 .G is easy to demonstrate very satisfactorily that the cranial pieces that 

 immediately enclose the cerebral masses are strictly vertebra, and pre- 

 sent the same essential structure as those of the spinal region. 



(2176.) That this is the case in the skull of a Reptile, no one, indeed, 

 who examines the subject can hesitate to admit ; but even in the Mam- 

 miferous cranium, where, from the enormous proportionate size of the 

 encephalon, the cranium is most distorted, it is not difficult to perceive 

 the relationship. 



(2177.) The cranial vertebrae are three in number : the occipital, the 

 parietal, and the frontal ; these are exhibited in the subjoined diagram, 

 after Carus, representing those of the Sheep. 



(2178.) The occipital vertebra (fig. 382, A) has for its body the basilar 

 portion ; the arches bound the foramen magnum laterally ; and above, 

 the spinous process, flattened out and expanded in proportion to the size 

 of those lobes of the brain and cerebellum which it defends, forms the 

 posterior portion of the skull. 



(2179.) The body of the second or parietal vertebra (B) is the body 

 of the sphenoid that is, more properly speaking, the posterior sphenoid 

 bone, whose large alae, curving upwards, meet the parietal, and thus an 

 arch is formed of sufficient span to cover the middle lobes of the cerebrum. 



