278 THE AMERICAN MONTHLY [Sept. 



saw on both sides of the tooth about midway of the 

 crown, and cut off the part with a pair of strong excising 

 or splitting forceps. The end of the pulp will then be 

 exposed without being hurt. At the apex of the root a 

 short piece is cut off in a similar way. For fixation of 

 the tissues, the tooth is placed in a saturated solution of 

 bichloride of mercury in water for about eight to twelve 

 hours, after which it is washed in running water for two 

 hours. 



To harden the tissues of the pulp, the tooth is then 

 placed in alcohol of low degree, the strength of which 

 must be gradually increased from 30 to 50 per cent., and 

 from 50 to 70 per cent., leaving the tooth from eight to 

 twelve hours in each of the three stages. From the 

 bichloride of mercury there will be left a black precipi- 

 tate on the specimens which can now be removed by 

 placing them for about twelve hours in 90 per cent, al- 

 cohol, to which IJ to 2 per cent, tincture of iodine has 

 been added. The iodine is removed by placing the spe- 

 cimens in pure alcohol until they recover their former 

 white appearance. After the process of hardening in al- 

 cohol, the teeth can be cut in two or three sections by 

 means of a fine, sharp scroll-saw. The next step is to 

 stain the specimens. There are a great number of dyes 

 used for staining preparations for microscopic studies. 

 Dr. Weil, in the description of his method, mentions a 

 great many, but he says he has obtained the best results 

 with " aqueous borax-carmine," prepared in the follow- 

 ing manner : — 



Eight grammes of borax is powdered in a mortar to- 

 gether with 2 grammes of carmine, and then mixed with 

 130 grammes of aq. dist. After twenty-four hours the 

 solution must be well filtered, and is then ready for use. 



The sections, when taken from alcohol, are washed in 

 running water for about fifteen minutes, and then trans- 

 jnitted to the dye for twelve to twenty, hours, iii which 



