200 ON THE PREPARVTION OF TOOTH SECTIONS. 



piece of buff leather with some putty powder on it. Afterwards, 

 take a piece of stout glass, put a little old, and consequently 

 tough, Canada balsam on it, warm it, and spread it a little larger 

 than your section. Let the balsam cool down until it is "tacky " ; 

 then press the polished side of the tooth into close contact with 

 the glass and clip. When quite cold the grinding may proceed, 

 as in the first part of the operation, till you get the required thin- 

 ness, when that side may also be polished. The hard balsam 

 round the section supports and protects the edges, so that they 

 will not be fractured and made jagged and untidy. B,y not 

 putting the tooth on to the glass plate until the balsam is some- 

 what cooled, you prevent the polished surface from being covered 

 with fine cracks, which might remind you of a dinner plate which 

 a careless cook has over-heated till the glaze is cracked in all 

 directions ; it also prevents the balsam from running into the 

 tubular structure of the dentine. 



As the process I adopt for mounting the section is appHcable 

 to all sections of hard tissues, I shall reserve my remarks upon it 

 till I have mentioned another plan of grinding down the rough 

 slices, which I can recommend from long experience on account 

 of its readiness, cleanliness, and the perfect parallelism of the 

 sections produced by it. Having a slice of dental or other hard 

 tissue of moderate thickness, place it between two plates of ground 

 glass, or between a plate of glass and a flat stone, such as an 

 Arkansas or Lake Washita stone, with water and a pinch of levi- 

 gated pumice powder, and by a rotary motion of the upper glass 

 gradually rub the section down till it is thin enough for examina- 

 tion with even the highest powers of the microscope. But 

 towards the end of the process be careful to watch it, for as the 

 glass and stone, or the two glasses, get closer together, and the 

 section thinner, one turn more of the upper glass will sometimes 

 result in the total disappearance of an hour's work, and you will 

 be eligible to take rank amongst beings of a very high order if an 

 explosion of your private opinion does not occur. Having ground 

 your section sufficiently thin by either of the before-mentioned 

 plans, it remains to be mounted in a suitable medium for 

 examination. 



