98 PREPARATION AND MOUNTING 



paratus as is needed in cutting sections of teeth, before described. 

 A fine saw, like those used for cutting brass, &c. ; two or three 

 flat files of different degrees of coarseness ; two flat " sharpening " 

 stones ; and a leather strop with putty-powder for polishing. As 

 thin a section as possible should first be cut from the part re- 

 quired by the aid of the fine saw ; and it is better when in this 

 state to soak it for some short time in camphene, ether, or some 

 other spirit to free it from all grease. With the aid of a file we 

 may now reduce it almost to the necessary degree of thinness, and 

 proceed as before recommended with teeth. The " sharpening " 

 stone will remove all scratches and marks sufficiently to allow it 

 to be examined with the microscope to see if it is ground thin 

 '.enough ; and if it is to be mounted dry we must polish it with 

 putty-powder and water upon the strop to as high a degree as 

 possible, and having washed all remains of polishing powder, &c., 

 from the section- we must place it upon the slide and finish it as 

 described in Chapter II. 



If the bone is not sufficiently hard in its nature to bear the above 

 method of handling whilst grinding and polishing as some are 

 far more brittle than others as thin a section as possible must 

 first be cut with the saw, and one surface ground and polished. 

 The piece must then be dried and united to the glass by heated 

 balsam in the same manner as shells, &c. After which the super- 

 abundance of balsam must be removed from the glass ; then rub 

 down upon the stone and strop as before. When the polishing is 

 completed the whole slide must be immersed in chloroform, ether, 

 or some other spirit, to release and cleanse the section, when it 

 may be mounted as the one above mentioned. 



Some have recommended a strong solution of isinglass to affix 

 the half-ground teeth or bones to the glass as causing them to 

 adhere very firmly and requiring no heat, and also being readily 

 detached when finished. 



The reason why the sections of bone are usually mounted dry 

 is that the " lacunce" bone cells, and canaliculi (resembling minute 

 canals) show their forms, &c., very perfectly in this state, as they 

 are hollow and contain air, whereas if they become filled with 

 liquid or balsam which does sometimes occur they become 

 almost indistinguishable. There are some dark specimens, however, 



