ON THE PREPARATION OF TOOTH SECTIONS. 203 



nothing so effectual as a saturated solution of common alum, with 

 about half a drachm of Hydrochloric acid added to each ounce 

 of solution. Steeping the tooth (or teeth) in this for about three 

 weeks leaves the tooth with a consistency of cork. If it is now 

 soaked in glycerine for a few days it may be embedded and cut 

 into thin sections by any of the usual microtomes. I prefer this 

 to either Picric or Chromic acid, because it does not stain the 

 hands, and I believe does not produce so much granularity as 

 the other processes do. 



Proceeding to the staining stage, Logwood is first on the list, 

 and can be prepared so as to be certain of working perfectly. The 

 way to prepare the extract is to dissolve it up in alcohol, add a few 

 drops of this to a saturated solution of potash alum, and, when 

 mixed, add a few crystals of phenol. This will give a brownish, 

 purple stain. Another very useful stain is Borax and Carmine ; 

 it will penetrate deeply into the tissue. The preparation consists 

 of J a drachm of Carmine and 2 drachms Borax, dissolved in 

 ' distilled water. Aniline dyes form most useful stains with these • 

 all sorts of shades can be brought out. Another useful stain is 

 Osmic Acid. The real use of Osmic Acid is to bring out any fat. 



In staining with Chloride of Gold, it really does not matter 

 whether the section be fresh or not, although many text books say 

 it is useless to attempt to stain tissues which have been deprived 

 of life more than an hour. The method described by Dr. Bodecker 

 has given the best results. He immerses the section, whether 

 cut from a decalcified tooth or ground down from a hard one, in 

 a solution of Carbonate of Soda for an hour. It is then placed 

 in a solution of Chloride of Gold, which must be neutral, and 

 left in the dark for another hour ; then put in the Carbonate of 

 Soda for a few moments, and transferred to a i per cent, solution 

 of Formic Acid, and kept warm over a bath for about an hour and 

 a half Finally, the section should be mounted in Glycerine Jelly 

 — not in Canada balsam. Sections which have been decalcified 

 by Chromic Acid take longer to stain than those that are fresh, 

 but the whole process only occupies from three to four hours, 

 instead of at least twenty-four hours as in the old method, and the 

 result will be found far more satisfactory. The usual needles, or 

 any sjeel instrument, must not be used for manipulating the sec- 



