INTRODUCTION. IxV 



more numerous, close-set, and extensively undulated, in a given 

 space, than in ordinary dentine, the organic bears a greater propor- 

 tion to the inorganic matter, than in the dentine of the teeth of 

 most other Mammals. The cement of the composite molar teeth 

 of the Ruminants and of the Elephant contains a little more organic 

 matter than the dentine does ; but in the cetaceous Dolphin it 

 contains a rather less proportion, and is consequently harder. 



The nerves of the teeth (1) are derived from the trigeminal, or 

 fifth pair, of which the second division supplies those of the upper 

 jaw, the third division those of the lower jaw. In the Human 

 Subject the three dental branches of the infra-orbital nerve intercom- 

 municate by their primary branches, from which, and from a rich 

 plexus formed by secondary branches upon the membrane lining the 

 antrum, two sets of nerves are sent off to the alveolar processes of 

 the upper jaw ; one set {rami dentales) supplies the teeth, the other 

 (rami gingivales) the osseous tissue and the gums ; the latter agree 

 in number with the intervals of the teeth, as the proper dental 

 nerves do with the teeth themselves. These two sets are not, 

 however, so distinct but that some intercommunications are established 

 between the fine branches sent off in their progress to the parts 

 they are specially destined to supply. The rami dentales take the 

 more direct course through the middle part of the osseous tissue 

 to the teeth ; penetrate the orifices of the fangs, and form a rich 

 plexus with rhomboidal meshes upon the coronal surface of the 

 pulp ; the peripheral elementary filaments returning into the plexus 

 by loops. 



In the lower jaw the dental nerve, besides supplying the proper 

 nerves to the teeth, also forms a rich plexus, in which it is joined 



(1) Swan, Demonstration of the Nerves of the Human Body, fol. 1830, pi. xii. Schu- 

 macher, Ueber die Nerven der Kiefer und des Zahnfleisches, 4to. 1839. 



