204 PRACTICAL HISTOLOGY. 



CHAPTER XIII. 



THE MOUTH AND PHARYNX. 



Mucous membrane of the mouth. Portions of 

 the lining membrane of the mouth are best prepared 

 in the way recommended for the skin, viz. by being 

 pinned out upon a cork and immersed for two or 

 three days in a mixture of equal parts of spirit and 

 half per cent, chromic acid solution. Sections of the 

 cheek or lip may also be readily prepared. 



THE TEETH. 



Preparation 1. Sections of hard tooth. No 



preparations exhibit the structure of the teeth better 

 than these. The hard tooth is ground down first on 

 one side and then on the other, until a thin section 

 only remains, and this is mounted in hard Canada 

 balsam in such a way that the air still remains in 

 the dentinal tubules, the lacunae of the cement, the 

 interglobular spaces, and other minute cavities that 

 may be present. The preparation is similar to that 

 of bone, but presents greater difficulty. Such speci- 

 mens may advantageously be purchased, for their 

 preparation involves the expenditure of a large 

 amount of time and labor; unless the use of a lapi- 

 dary's wheel can be obtained, when the process is 

 much facilitated. They should in every case be 

 studied first with a low power, and afterwards with 

 a high power objective. 



Preparation 2. Sections of softened tooth. 

 But, in addition to the facts which the hard spe- 

 cimens will show, various others may be made out 



