OF MICROSCOPIC OBJECTS. 149 



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 superabundance of balsam 

 must be removed from the glass; then rub down upon the stone 

 and strop as before. Great care must be taken that the canals 

 "be not filled during the process with the dust of the bone, 

 or of the polishing material. Dr. Beale, in the journal of 

 the Q. M. 0. takes occasion to say " that he cannot admit 

 that the best way of preparing such sections is by grinding 

 down, since it is too liable to fill the canals with debris" He 

 recommends that a fresh bone be taken and a small slice 

 cut off by a strong sharp knife. This is then to be im- 

 mersed in carmine dissolved in ammonia the ammonia 

 "being first neutralized by acetic acid. The walls of the 

 Tessels which penetrate the lacuna* and eanaliculi are by 

 this means stained crimson, and thus the true structure of 

 bone is rendered visible. 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 eanaliculi (re- 

 sembling minute canals) show their forms, &c., very per- 

 fectly 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, where the cells are 

 already filled with other matter, and it is well to mount these 

 with balsam and so gain a greater degree of transparency. 



