PREPARING SECTIONS OF TEETH. 27 



and is a great advantage, as specimens are in no way liarmed for 

 the demonstration of micro-organisms. When the tissue is pro- 

 perly hardened, pour off the hardening agent and wash well with 

 water to get rid of the reagent, transfer to weak spirit for a day or 

 two (2 parts spirit, i water, stir), then into pure spirit. 



Sections of Pulp.— Crush a newly extracted tooth in a vice or 

 with a hammer, and select several pieces of dentine with portions 

 of pulp adherent to them, then immerse in staining fluid, cover 

 with a glass capsule, and leave in a warm place for a couple of 

 days. Then pour the fluid off and wash the specimens in a solu- 

 tion made of strong glycerine 2 parts, distilled water r part, and 

 leave for a couple of hours to soak. To enable the tissues to 

 regain their original volume, transfer them to a solution of 5 drops 

 acetic acid to i ounce of strong glycerine, and leave in the fluid 

 for four days. 



Another method and one recommended by Dr. Bodecker for 

 preparing pulp tissue is to immediately place the tooth after 

 removal from the mouth in a one-sixth to one-half per cent, 

 chromic acid. To this mixture add, after the third or fourth day 

 after decalcification, a few drops of dilute hydrochloric acid. It is 

 important to use a large quantity of the liquid and renew every 

 six or eight days. After the teeth have been hardening and decal- 

 cifying for a few weeks, the peripheral portion of the dentine will 

 become sufficiently soft to be cut with a razor. When the hard 

 portions of the dentine are reached by the cutting instruments, the 

 extraction of the lime-salts must again be continued in the manner 

 described above until the pulp cavity is reached. If care is used, 

 the tooth, especially the anterior, can be split with a strong pair of 

 excising forceps. Then take a half per cent, solution of sodium 

 chloride in distilled water (warm), and place on the pulp and drop 

 it without handling into the stain, carmine, logwood, fuchsin, 

 hyperosmic acid, picro-indigo, or chloride of gold, half per cent., etc. 



Pulp sections, if thin, after hardening in chromic acid, can, if 

 first washed in distilled water, be stained with gold chloride, leaving 

 the stain on the tissue for twenty to thirty minutes, when they 

 should again be washed in distilled water and exposed to daylight. 

 In a few hours the colour of the fresh tissue changes to a bright 

 violet colour, whilst the chromic acid pulp is of a brownish violet. 



