T. C. WHITE ON SECTIONS OF HARD TISSUES. 173 



retaining its teeth. In this case I soaked the jaw in snch a way as to 

 saturate it with Canada Balsam in Benzole ; this, when it had evapo- 

 rated, filled every interstice with hard balsam, and so retained the 

 teeth in position while the grinding was performed. 



I wish now to speak of the various appearances observed in sec- 

 tions of the teeth, as it may prove useful to many here who may 

 feel inclined to make sections of some sent here for distribution this 

 evening. 



The tooth most easily worked is that removed from a child, a 

 temporary tooth ; the structure approaches most nearly to the normal 

 condition, and such a section will present the following appearance : 

 in the centre, a cavity occupied in the recent state by a soft fleshy 

 mass — what is popularly known as the nerve, but in reality being 

 composed of the minute ramifications of the nerve, vein, and artery, 

 supported by fibrous tissue ; on the outer side of this, and making 

 up the greater part of the tooth, is the dentine, or the tooth bone 

 proper, as it may be termed ; this consists of a number of fine tubes, 

 about l0 -* 00 of an inch in diameter placed closely side by side, and 

 radiating everywhere at right angles to the walls of the central pulp 

 cavity. Covering the upper part as a protection, may be seen the 

 dense, almost inorganic enamel, whose crystalline prisms stand 

 vertically to the surface of the dentine, and covering that part of 

 the tooth which protrudes through the gum. On the lower part of 

 the fang, and thickest near the apex of the root, the cementum will 

 be found with its lacunae and straggling canaliculi. Such, roughly, 

 is a sketch of the appearance presented in a healthy, well-developed 

 tooth ; but age and various disturbing causes will interfere "with or 

 alter the appearance here described, and I shall now attempt to give 

 you a description of the changes from the normal condition which are 

 usually met with. 



Some teeth are obliged to be removed, especially in old age, on 

 account of getting loose and barely hanging in the mouth; these teeth 

 seldom show any decided appearance of decay, and are generally 

 extracted entire. 



Upon making a section of such a tooth as this, the apex of the 

 tooth will be found transparent like horn or tortoiseshell ; such teeth 

 are to all intents and purposes dead members, and hence the loosen- 

 ing. The dentinal tubes are filled up, and become consolidated by a 

 deposition of calcareous matter, and should the tooth be ground 

 down on its surface by mastication, the upper part of the pulp 



Journ. Q. M. C. No. 14. n 



