370 BIOLOGY. 



like the anterior canal, viscera dissimilar in kind to bone ; 

 the one including the spinal cord, the other vessels, 

 intestine, and lung. 



2105. The bony cysts that have originated through 

 constriction do not all harden into calcareous matter, but 

 they remain as alternating membranous cysts. Between 

 the rings there are permanent cysts. The membranous 

 cysts form the joint, or articular capsule. An articular 

 capsule is a bone which has remained soft. 



2106. This change in the ossific process takes place 

 through the attachment of muscles, concerning which 

 we shall treat in the sequel. 



2107. The whole osseous system is consequently a 

 symmetrical arrangement of several polar cysts and rings. 



2108. The vertebra is not a single ring, but is at 

 once a tolerably compound osseous system. The whole 

 osseous system is nothing but a vertebra repeated. 



2109. The number of the vertebra necessarily con- 

 forms to that of the pairs of nerves or ganglia of the 

 spinal cord ; for they are indeed only the periphery or 

 envelope of the latter. The number of nerves is, how- 

 ever, adapted to that of the organs, which they have to 

 take care of. 



2110. Now, the nervous organs are the senses. There 

 are consequently as many divisions of vertebra? as there 

 are senses. Thus there are vertebrae appertaining re- 

 spectively to the senses of touch, taste, smell, hearing, 



! and sight. Now as the four latter senses make up the 



1 head, but that of touch or feeling is distributed over the 



5 whole body, and superintended by the spinal nerves, the 



vertebras thus divide into two principal sections, into 



vertebrae of the head and trunk. The number of cephalic 



vertebrae is 4 ; namely, nasal, ocular, lingual, and auditory 



vertebrae. 



2111. To a perfect vertebra belong at least five 

 pieces, namely, the body, in front the two ribs, behind 

 the two arches or spinous processes ; every vertebra of 

 the head consists therefore of five pieces also. In those 

 vertebrae which are removed from the respiratory organ, 



