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excellent results, but I have found it attended by two drawbacks, 1st, the 

 enamel of the teeth was so hard that it soon wore ont all the serrations of 

 my saw, and it also took a long time to cut the section. The next draw- 

 back to this plan was, that however carefully the section was prepared 

 when it came to the process of being dissolved off the glass in spirit pre- 

 paratory to mounting, the spirit carried the balsam into the structure, and 

 obliterated all its detail, if not at the time, certainly at some time after. I 

 got over these difficulties in this manner : Having plenty of materials at my 

 disposal I contented myself by making one section out of each tooth, grind- 

 ing the side of the tooth against a corundum wheel in a dentist's lathe, 

 sticking the ground side on to a piece of glass with very hard balsam, and 

 then grinding the other side in a similar manner till the section was 

 moderately thin. I then detached it from the glass and putting the 

 section between two plates of ground glass, I rubbed it with the aid of finely- 

 powdered pumice stone and water till I got it of the required thinness — it 

 was necessary to examine it from time to time under the microscope in 

 order to avoid cutting it too thin, for I have rubbed sections so thin 

 that with one turn more of the upper plate of ground glass I have 

 caused the section to disappear altogether. I think, therefore, it is de- 

 sirable to urge this precaution on your attention. The plan I have 

 described not only ensures perfect parallelism between the two surfaces 

 of the section, but also allows of your getting it much thinner than 

 the plan usually recommended, and it has this further advantage to re- 

 commend it, which leads me to the method by which I overcome my 

 second difficulty, viz., the balsam running in and obliterating the struc- 

 ture. After I have got the section as thin as I wish I cleanse it thoroughly 

 from the dibris it has acquired in the grinding, and put it away in dis- 

 tilled water until I require to mount it in balsam. I then take it out 

 of the distilled water, dry its surfaces by wiping them with a warm and 

 clean finger, and then mount in cold balsam ; the internal structure 

 whether lacmree, canaliculi, or dentinal tubules are occluded by the dis- 

 tilled water, and the balsam is prevented from running in. I have, however, 

 lately received the details of a plan from Mr. Ady which will, I imagine, 

 entirely surpass the method I have described, but as I have had no ex- 

 perience in its working, I will ask Mr. Ady, who is present, to give some 

 detail of his plan. 



" The making of bone sections is carried ont in the same way as that of 

 teeth, but it is much easier, owing to the absence of the hard enamel. The 

 same plan may also be adopted for making sections of shell, the stones of 

 fruit, and cocoa-nut shell. Sections of Echinus spines are difficult to make 

 on account of their brittleness, but if they are soaked in a solution of hard 

 balsam in benzol, and then dried, they can with care, be reduced to very 

 thin sections without fracture. 



" For this purpose I should prefer to use some of the older pieces of ground 

 glass, such as have by use become partly polished, as there is then no drag 

 of the grain against the brittle cells of the spine. This same plan may 

 also be adopted for making sections of the entire jaw of small animals, 



