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NOTES. 



On Preparing and Mounting Sections of Hard Tissues. 



Some ten years since there appeared in " Silliman's Journal" a note by Dr. 

 Christopher Johnstone, " On Preparing and Mounting Hard Tissues for the 

 Microscope," which describes a method of procedure which is worth the notice 

 of our members We therefore give a summary of its contents. 



A microscopic section should be as thin as the structure of the object will 

 allow, of uniform thickness, and polished on both sides, whether it be mounted 

 in the dry way or in balsam. The following requisites should be provided : — 



1. A coarse and fine Kansas hone, dressed flat with fine emery. 



2. A fine Stubb's dentist's file (or a watchmaker's superfijie potence file) . 



3. A thin dividing file and fine saw. 



4. Some Kussian isinglass boiled, strained, and mixed with alcohol, sufficient 



to form a tolerably thick jelly when cold. 



5. Canada balsam. 



6. Glass slides. 



7. Thin glass for covering. 



8. One ounce of chloroform. 



9. One ounce of strong aqua ammonia, 



10. Some pieces of thick plate glass, one inch square, or one by two inches. 



11. Thin French letter paper, of which 500 or more leaves are required to fill 



up the space of an inch- 

 Coarse sections may be obtained with the saw or dividing file (excepting 

 BiUcified substances), but these instruments are not apj)licable to longitudinal 

 sections of small human or other teeth, small bones, &c. These should be first 

 ground upon the coarse hone with water, until the surface coincides with the 

 intended plane, then washed carefully, finished upon the finer hone, and then 

 polished upon soft Hnen, stretched upon a smooth block. 



If the object be too small to admit of handling, it should be fastened upon a 

 piece of glass with isinglass, or, what is better, upon thin paper well glued with 

 the same substance upon glass ; and a piece of thick paper or visiting card, 

 perforated with a free aperture for the object, must be attached to the first 

 paper. This is the guard down to which the specimen must be ground with oil; 

 and its thickness and the disposal of the object requires the exercise of good 

 judgment. Hot water will release everything, and chloroform (or benzine) 

 remove the grease from the specimen, which, like the former one ground with 

 water, is ready for the second part of the process. 



Now cover the surface of a piece of the plate glass with thin French letter 

 paper; next apply a paper guard, as before stated, but not thicker for teeth and 

 bone than l-500th inch ; then trace a few lines with a lead pencil upon the 

 first paper, in the little space left in the guard, so that the increasing trans- 

 parency of a specimen in course of preparation may be observed ; and, finally, 

 moisten the space with isinglass to the extent of the object, which must be 

 delicately brushed over on the ground surface and at the edges with tolerably 

 thin isinglass before it is cemented in its place. Gentle pressure must now be 

 applied and maintained by a wire spring or other means. 



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